Linux Virtualization - Sep 2023 - [PATCH vfio 11/11] vfio/virtio: Introduce a vfio driver over virtio devices

Introduce a vfio driver over virtio devices to support the legacy
interface functionality for VFs.

Background, from the virtio spec [1].
--------------------------------------------------------------------
In some systems, there is a need to support a virtio legacy driver with
a device that does not directly support the legacy interface. In such
scenarios, a group owner device can provide the legacy interface
functionality for the group member devices. The driver of the owner
device can then access the legacy interface of a member device on behalf
of the legacy member device driver.

For example, with the SR-IOV group type, group members (VFs) can not
present the legacy interface in an I/O BAR in BAR0 as expected by the
legacy pci driver. If the legacy driver is running inside a virtual
machine, the hypervisor executing the virtual machine can present a
virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
legacy driver accesses to this I/O BAR and forwards them to the group
owner device (PF) using group administration commands.
--------------------------------------------------------------------

Specifically, this driver adds support for a virtio-net VF to be exposed
as a transitional device to a guest driver and allows the legacy IO BAR
functionality on top.

This allows a VM which uses a legacy virtio-net driver in the guest to
work transparently over a VF which its driver in the host is that new
driver.

The driver can be extended easily to support some other types of virtio
devices (e.g virtio-blk), by adding in a few places the specific type
properties as was done for virtio-net.

For now, only the virtio-net use case was tested and as such we introduce
the support only for such a device.

Practically,
Upon probing a VF for a virtio-net device, in case its PF supports
legacy access over the virtio admin commands and the VF doesn't have BAR
0, we set some specific 'vfio_device_ops' to be able to simulate in SW a
transitional device with I/O BAR in BAR 0.

The existence of the simulated I/O bar is reported later on by
overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
exposes itself as a transitional device by overwriting some properties
upon reading its config space.

Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
guest may use it via read/write calls according to the virtio
specification.

Any read/write towards the control parts of the BAR will be captured by
the new driver and will be translated into admin commands towards the
device.

Any data path read/write access (i.e. virtio driver notifications) will
be forwarded to the physical BAR which its properties were supplied by
the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.

With that code in place a legacy driver in the guest has the look and
feel as if having a transitional device with legacy support for both its
control and data path flows.

[1]
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c

Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
---
 MAINTAINERS                      |   6 +
 drivers/vfio/pci/Kconfig         |   2 +
 drivers/vfio/pci/Makefile        |   2 +
 drivers/vfio/pci/virtio/Kconfig  |  15 +
 drivers/vfio/pci/virtio/Makefile |   4 +
 drivers/vfio/pci/virtio/cmd.c    |   4 +-
 drivers/vfio/pci/virtio/cmd.h    |   8 +
 drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
 8 files changed, 585 insertions(+), 2 deletions(-)
 create mode 100644 drivers/vfio/pci/virtio/Kconfig
 create mode 100644 drivers/vfio/pci/virtio/Makefile
 create mode 100644 drivers/vfio/pci/virtio/main.c

diff --git a/MAINTAINERS b/MAINTAINERS
index bf0f54c24f81..5098418c8389 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
 S:	Maintained
 F:	drivers/vfio/pci/mlx5/
 
+VFIO VIRTIO PCI DRIVER
+M:	Yishai Hadas <yishaih at nvidia.com>
+L:	kvm at vger.kernel.org
+S:	Maintained
+F:	drivers/vfio/pci/virtio
+
 VFIO PCI DEVICE SPECIFIC DRIVERS
 R:	Jason Gunthorpe <jgg at nvidia.com>
 R:	Yishai Hadas <yishaih at nvidia.com>
diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
index 8125e5f37832..18c397df566d 100644
--- a/drivers/vfio/pci/Kconfig
+++ b/drivers/vfio/pci/Kconfig
@@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
 
 source "drivers/vfio/pci/pds/Kconfig"
 
+source "drivers/vfio/pci/virtio/Kconfig"
+
 endmenu
diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
index 45167be462d8..046139a4eca5 100644
--- a/drivers/vfio/pci/Makefile
+++ b/drivers/vfio/pci/Makefile
@@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
 obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
 
 obj-$(CONFIG_PDS_VFIO_PCI) += pds/
+
+obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
diff --git a/drivers/vfio/pci/virtio/Kconfig b/drivers/vfio/pci/virtio/Kconfig
new file mode 100644
index 000000000000..89eddce8b1bd
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config VIRTIO_VFIO_PCI
+        tristate "VFIO support for VIRTIO PCI devices"
+        depends on VIRTIO_PCI
+        select VFIO_PCI_CORE
+        help
+          This provides support for exposing VIRTIO VF devices using the VFIO
+          framework that can work with a legacy virtio driver in the guest.
+          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs shall
+          not indicate I/O Space.
+          As of that this driver emulated I/O BAR in software to let a VF be
+          seen as a transitional device in the guest and let it work with
+          a legacy driver.
+
+          If you don't know what to do here, say N.
diff --git a/drivers/vfio/pci/virtio/Makefile b/drivers/vfio/pci/virtio/Makefile
new file mode 100644
index 000000000000..584372648a03
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Makefile
@@ -0,0 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
+virtio-vfio-pci-y := main.o cmd.o
+
diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
index f068239cdbb0..aea9d25fbf1d 100644
--- a/drivers/vfio/pci/virtio/cmd.c
+++ b/drivers/vfio/pci/virtio/cmd.c
@@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
 {
 	struct virtio_device *virtio_dev  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
-	struct virtio_admin_cmd_data_lr_write *in;
+	struct virtio_admin_cmd_legacy_wr_data *in;
 	struct scatterlist in_sg;
 	struct virtio_admin_cmd cmd = {};
 	int ret;
@@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
 {
 	struct virtio_device *virtio_dev  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
-	struct virtio_admin_cmd_data_lr_read *in;
+	struct virtio_admin_cmd_legacy_rd_data *in;
 	struct scatterlist in_sg, out_sg;
 	struct virtio_admin_cmd cmd = {};
 	int ret;
diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
index c2a3645f4b90..347b1dc85570 100644
--- a/drivers/vfio/pci/virtio/cmd.h
+++ b/drivers/vfio/pci/virtio/cmd.h
@@ -13,7 +13,15 @@
 
 struct virtiovf_pci_core_device {
 	struct vfio_pci_core_device core_device;
+	u8 bar0_virtual_buf_size;
+	u8 *bar0_virtual_buf;
+	/* synchronize access to the virtual buf */
+	struct mutex bar_mutex;
 	int vf_id;
+	void __iomem *notify_addr;
+	u32 notify_offset;
+	u8 notify_bar;
+	u8 pci_cmd_io :1;
 };
 
 int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
diff --git a/drivers/vfio/pci/virtio/main.c b/drivers/vfio/pci/virtio/main.c
new file mode 100644
index 000000000000..2486991c49f3
--- /dev/null
+++ b/drivers/vfio/pci/virtio/main.c
@@ -0,0 +1,546 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights reserved
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/pci.h>
+#include <linux/pm_runtime.h>
+#include <linux/types.h>
+#include <linux/uaccess.h>
+#include <linux/vfio.h>
+#include <linux/vfio_pci_core.h>
+#include <linux/virtio_pci.h>
+#include <linux/virtio_net.h>
+#include <linux/virtio_pci_modern.h>
+
+#include "cmd.h"
+
+#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
+#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
+
+static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device *virtvdev,
+				 loff_t pos, char __user *buf,
+				 size_t count, bool read)
+{
+	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
+	u16 opcode;
+	int ret;
+
+	mutex_lock(&virtvdev->bar_mutex);
+	if (read) {
+		opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
+			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
+			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
+		ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
+					   count, bar0_buf + pos);
+		if (ret)
+			goto out;
+		if (copy_to_user(buf, bar0_buf + pos, count))
+			ret = -EFAULT;
+		goto out;
+	}
+
+	if (copy_from_user(bar0_buf + pos, buf, count)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
+			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
+			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;
+	ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
+				    bar0_buf + pos);
+out:
+	mutex_unlock(&virtvdev->bar_mutex);
+	return ret;
+}
+
+static int
+translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
+			    loff_t pos, char __user *buf,
+			    size_t count, bool read)
+{
+	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
+	u16 queue_notify;
+	int ret;
+
+	if (pos + count > virtvdev->bar0_virtual_buf_size)
+		return -EINVAL;
+
+	switch (pos) {
+	case VIRTIO_PCI_QUEUE_NOTIFY:
+		if (count != sizeof(queue_notify))
+			return -EINVAL;
+		if (read) {
+			ret = vfio_pci_ioread16(core_device, true, &queue_notify,
+						virtvdev->notify_addr);
+			if (ret)
+				return ret;
+			if (copy_to_user(buf, &queue_notify,
+					 sizeof(queue_notify)))
+				return -EFAULT;
+			break;
+		}
+
+		if (copy_from_user(&queue_notify, buf, count))
+			return -EFAULT;
+
+		ret = vfio_pci_iowrite16(core_device, true, queue_notify,
+					 virtvdev->notify_addr);
+		break;
+	default:
+		ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
+	}
+
+	return ret ? ret : count;
+}
+
+static bool range_contains_range(loff_t range1_start, size_t count1,
+				 loff_t range2_start, size_t count2,
+				 loff_t *start_offset)
+{
+	if (range1_start <= range2_start &&
+	    range1_start + count1 >= range2_start + count2) {
+		*start_offset = range2_start - range1_start;
+		return true;
+	}
+	return false;
+}
+
+static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
+					char __user *buf, size_t count,
+					loff_t *ppos)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	loff_t copy_offset;
+	__le32 val32;
+	__le16 val16;
+	u8 val8;
+	int ret;
+
+	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
+	if (ret < 0)
+		return ret;
+
+	if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
+				 &copy_offset)) {
+		val16 = cpu_to_le16(0x1000);
+		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+			return -EFAULT;
+	}
+
+	if (virtvdev->pci_cmd_io &&
+	    range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
+				 &copy_offset)) {
+		if (copy_from_user(&val16, buf, sizeof(val16)))
+			return -EFAULT;
+		val16 |= cpu_to_le16(PCI_COMMAND_IO);
+		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+			return -EFAULT;
+	}
+
+	if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
+				 &copy_offset)) {
+		/* Transional needs to have revision 0 */
+		val8 = 0;
+		if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
+			return -EFAULT;
+	}
+
+	if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
+				 &copy_offset)) {
+		val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
+		if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
+			return -EFAULT;
+	}
+
+	if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
+				 &copy_offset)) {
+		/* Transitional devices use the PCI subsystem device id as
+		 * virtio device id, same as legacy driver always did.
+		 */
+		val16 = cpu_to_le16(VIRTIO_ID_NET);
+		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
+			return -EFAULT;
+	}
+
+	return count;
+}
+
+static ssize_t
+virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
+		       size_t count, loff_t *ppos)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	struct pci_dev *pdev = virtvdev->core_device.pdev;
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	int ret;
+
+	if (!count)
+		return 0;
+
+	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
+		return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
+
+	if (index != VFIO_PCI_BAR0_REGION_INDEX)
+		return vfio_pci_core_read(core_vdev, buf, count, ppos);
+
+	ret = pm_runtime_resume_and_get(&pdev->dev);
+	if (ret) {
+		pci_info_ratelimited(pdev, "runtime resume failed %d\n",
+				     ret);
+		return -EIO;
+	}
+
+	ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
+	pm_runtime_put(&pdev->dev);
+	return ret;
+}
+
+static ssize_t
+virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user *buf,
+			size_t count, loff_t *ppos)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	struct pci_dev *pdev = virtvdev->core_device.pdev;
+	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
+	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+	int ret;
+
+	if (!count)
+		return 0;
+
+	if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
+		loff_t copy_offset;
+		u16 cmd;
+
+		if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
+					 &copy_offset)) {
+			if (copy_from_user(&cmd, buf + copy_offset, sizeof(cmd)))
+				return -EFAULT;
+			virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
+		}
+	}
+
+	if (index != VFIO_PCI_BAR0_REGION_INDEX)
+		return vfio_pci_core_write(core_vdev, buf, count, ppos);
+
+	ret = pm_runtime_resume_and_get(&pdev->dev);
+	if (ret) {
+		pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
+		return -EIO;
+	}
+
+	ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf, count,
false);
+	pm_runtime_put(&pdev->dev);
+	return ret;
+}
+
+static int
+virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
+				   unsigned int cmd, unsigned long arg)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
+	void __user *uarg = (void __user *)arg;
+	struct vfio_region_info info = {};
+
+	if (copy_from_user(&info, uarg, minsz))
+		return -EFAULT;
+
+	if (info.argsz < minsz)
+		return -EINVAL;
+
+	switch (info.index) {
+	case VFIO_PCI_BAR0_REGION_INDEX:
+		info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
+		info.size = virtvdev->bar0_virtual_buf_size;
+		info.flags = VFIO_REGION_INFO_FLAG_READ |
+			     VFIO_REGION_INFO_FLAG_WRITE;
+		return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
+	default:
+		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+	}
+}
+
+static long
+virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int cmd,
+			     unsigned long arg)
+{
+	switch (cmd) {
+	case VFIO_DEVICE_GET_REGION_INFO:
+		return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
+	default:
+		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
+	}
+}
+
+static int
+virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
+{
+	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
+	int ret;
+
+	/* Setup the BAR where the 'notify' exists to be used by vfio as well
+	 * This will let us mmap it only once and use it when needed.
+	 */
+	ret = vfio_pci_core_setup_barmap(core_device,
+					 virtvdev->notify_bar);
+	if (ret)
+		return ret;
+
+	virtvdev->notify_addr = core_device->barmap[virtvdev->notify_bar] +
+			virtvdev->notify_offset;
+	return 0;
+}
+
+static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	struct vfio_pci_core_device *vdev = &virtvdev->core_device;
+	int ret;
+
+	ret = vfio_pci_core_enable(vdev);
+	if (ret)
+		return ret;
+
+	if (virtvdev->bar0_virtual_buf) {
+		/* upon close_device() the vfio_pci_core_disable() is called
+		 * and will close all the previous mmaps, so it seems that the
+		 * valid life cycle for the 'notify' addr is per open/close.
+		 */
+		ret = virtiovf_set_notify_addr(virtvdev);
+		if (ret) {
+			vfio_pci_core_disable(vdev);
+			return ret;
+		}
+	}
+
+	vfio_pci_core_finish_enable(vdev);
+	return 0;
+}
+
+static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
+{
+	vfio_pci_core_close_device(core_vdev);
+}
+
+static int virtiovf_get_device_config_size(unsigned short device)
+{
+	switch (device) {
+	case 0x1041:
+		/* network card */
+		return offsetofend(struct virtio_net_config, status);
+	default:
+		return 0;
+	}
+}
+
+static int virtiovf_read_notify_info(struct virtiovf_pci_core_device *virtvdev)
+{
+	u64 offset;
+	int ret;
+	u8 bar;
+
+	ret = virtiovf_cmd_lq_read_notify(virtvdev,
+				VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
+				&bar, &offset);
+	if (ret)
+		return ret;
+
+	virtvdev->notify_bar = bar;
+	virtvdev->notify_offset = offset;
+	return 0;
+}
+
+static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+	struct pci_dev *pdev;
+	int ret;
+
+	ret = vfio_pci_core_init_dev(core_vdev);
+	if (ret)
+		return ret;
+
+	pdev = virtvdev->core_device.pdev;
+	virtvdev->vf_id = pci_iov_vf_id(pdev);
+	if (virtvdev->vf_id < 0)
+		return -EINVAL;
+
+	ret = virtiovf_read_notify_info(virtvdev);
+	if (ret)
+		return ret;
+
+	virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
+		VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
+		virtiovf_get_device_config_size(pdev->device);
+	virtvdev->bar0_virtual_buf = kzalloc(virtvdev->bar0_virtual_buf_size,
+					     GFP_KERNEL);
+	if (!virtvdev->bar0_virtual_buf)
+		return -ENOMEM;
+	mutex_init(&virtvdev->bar_mutex);
+	return 0;
+}
+
+static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
+{
+	struct virtiovf_pci_core_device *virtvdev = container_of(
+		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
+
+	kfree(virtvdev->bar0_virtual_buf);
+	vfio_pci_core_release_dev(core_vdev);
+}
+
+static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
+	.name = "virtio-transitional-vfio-pci",
+	.init = virtiovf_pci_init_device,
+	.release = virtiovf_pci_core_release_dev,
+	.open_device = virtiovf_pci_open_device,
+	.close_device = virtiovf_pci_close_device,
+	.ioctl = virtiovf_vfio_pci_core_ioctl,
+	.read = virtiovf_pci_core_read,
+	.write = virtiovf_pci_core_write,
+	.mmap = vfio_pci_core_mmap,
+	.request = vfio_pci_core_request,
+	.match = vfio_pci_core_match,
+	.bind_iommufd = vfio_iommufd_physical_bind,
+	.unbind_iommufd = vfio_iommufd_physical_unbind,
+	.attach_ioas = vfio_iommufd_physical_attach_ioas,
+};
+
+static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
+	.name = "virtio-acc-vfio-pci",
+	.init = vfio_pci_core_init_dev,
+	.release = vfio_pci_core_release_dev,
+	.open_device = virtiovf_pci_open_device,
+	.close_device = virtiovf_pci_close_device,
+	.ioctl = vfio_pci_core_ioctl,
+	.device_feature = vfio_pci_core_ioctl_feature,
+	.read = vfio_pci_core_read,
+	.write = vfio_pci_core_write,
+	.mmap = vfio_pci_core_mmap,
+	.request = vfio_pci_core_request,
+	.match = vfio_pci_core_match,
+	.bind_iommufd = vfio_iommufd_physical_bind,
+	.unbind_iommufd = vfio_iommufd_physical_unbind,
+	.attach_ioas = vfio_iommufd_physical_attach_ioas,
+};
+
+static bool virtiovf_bar0_exists(struct pci_dev *pdev)
+{
+	struct resource *res = pdev->resource;
+
+	return res->flags ? true : false;
+}
+
+#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
+	(BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
+	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
+
+static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
+{
+	int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
+	u8 *buf;
+	int ret;
+
+	/* Only virtio-net is supported/tested so far */
+	if (pdev->device != 0x1041)
+		return false;
+
+	buf = kzalloc(buf_size, GFP_KERNEL);
+	if (!buf)
+		return false;
+
+	ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
+	if (ret)
+		goto end;
+
+	if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP) !+	
VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
+		ret = -EOPNOTSUPP;
+		goto end;
+	}
+
+	/* confirm the used commands */
+	memset(buf, 0, buf_size);
+	*(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
+	ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
+
+end:
+	kfree(buf);
+	return ret ? false : true;
+}
+
+static int virtiovf_pci_probe(struct pci_dev *pdev,
+			      const struct pci_device_id *id)
+{
+	const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
+	struct virtiovf_pci_core_device *virtvdev;
+	int ret;
+
+	if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev)
&&
+	    !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
+		ops = &virtiovf_acc_vfio_pci_tran_ops;
+
+	virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
+				     &pdev->dev, ops);
+	if (IS_ERR(virtvdev))
+		return PTR_ERR(virtvdev);
+
+	dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
+	ret = vfio_pci_core_register_device(&virtvdev->core_device);
+	if (ret)
+		goto out;
+	return 0;
+out:
+	vfio_put_device(&virtvdev->core_device.vdev);
+	return ret;
+}
+
+static void virtiovf_pci_remove(struct pci_dev *pdev)
+{
+	struct virtiovf_pci_core_device *virtvdev =
dev_get_drvdata(&pdev->dev);
+
+	vfio_pci_core_unregister_device(&virtvdev->core_device);
+	vfio_put_device(&virtvdev->core_device.vdev);
+}
+
+static const struct pci_device_id virtiovf_pci_table[] = {
+	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET, PCI_ANY_ID)
},
+	{}
+};
+
+MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
+
+static struct pci_driver virtiovf_pci_driver = {
+	.name = KBUILD_MODNAME,
+	.id_table = virtiovf_pci_table,
+	.probe = virtiovf_pci_probe,
+	.remove = virtiovf_pci_remove,
+	.err_handler = &vfio_pci_core_err_handlers,
+	.driver_managed_dma = true,
+};
+
+module_pci_driver(virtiovf_pci_driver);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Yishai Hadas <yishaih at nvidia.com>");
+MODULE_DESCRIPTION(
+	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device
family");
-- 
2.27.0

>  MAINTAINERS                      |   6 +
>  drivers/vfio/pci/Kconfig         |   2 +
>  drivers/vfio/pci/Makefile        |   2 +
>  drivers/vfio/pci/virtio/Kconfig  |  15 +
>  drivers/vfio/pci/virtio/Makefile |   4 +
>  drivers/vfio/pci/virtio/cmd.c    |   4 +-
>  drivers/vfio/pci/virtio/cmd.h    |   8 +
>  drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
>  8 files changed, 585 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/vfio/pci/virtio/Kconfig
>  create mode 100644 drivers/vfio/pci/virtio/Makefile
>  create mode 100644 drivers/vfio/pci/virtio/main.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bf0f54c24f81..5098418c8389 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
>  S:	Maintained
>  F:	drivers/vfio/pci/mlx5/
>  
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <yishaih at nvidia.com>
> +L:	kvm at vger.kernel.org
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>  VFIO PCI DEVICE SPECIFIC DRIVERS
>  R:	Jason Gunthorpe <jgg at nvidia.com>
>  R:	Yishai Hadas <yishaih at nvidia.com>
Tying two subsystems together like this is going to cause pain when
merging. God forbid there's something e.g. virtio net specific
(and there's going to be for sure) - now we are talking 3 subsystems.

Case in point all other virtio drivers are nicely grouped, have a common
mailing list etc etc.  This one is completely separate to the point
where people won't even remember to copy the virtio mailing list.


diff --git a/drivers/vfio/pci/virtio/Kconfig b/drivers/vfio/pci/virtio/Kconfig
new file mode 100644
index 000000000000..89eddce8b1bd
--- /dev/null
+++ b/drivers/vfio/pci/virtio/Kconfig
@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config VIRTIO_VFIO_PCI
+        tristate "VFIO support for VIRTIO PCI devices"
+        depends on VIRTIO_PCI
+        select VFIO_PCI_CORE
+        help
+          This provides support for exposing VIRTIO VF devices using the VFIO
+          framework that can work with a legacy virtio driver in the guest.
+          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs shall
+          not indicate I/O Space.
+          As of that this driver emulated I/O BAR in software to let a VF be
+          seen as a transitional device in the guest and let it work with
+          a legacy driver.
+
+          If you don't know what to do here, say N.

I don't promise we'll remember to poke at vfio if we tweak something
in the virtio kconfig.

-- 
MST

On Thu, Sep 21, 2023 at 03:40:40PM +0300, Yishai Hadas
wrote:
> +#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
> +#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
This is exactly part of VIRTIO_PCI_CONFIG_OFF duplicated.

-- 
MST

On Thu, 21 Sep 2023 15:40:40 +0300
Yishai Hadas <yishaih at nvidia.com> wrote:
> Introduce a vfio driver over virtio devices to support the legacy
> interface functionality for VFs.
> 
> Background, from the virtio spec [1].
> --------------------------------------------------------------------
> In some systems, there is a need to support a virtio legacy driver with
> a device that does not directly support the legacy interface. In such
> scenarios, a group owner device can provide the legacy interface
> functionality for the group member devices. The driver of the owner
> device can then access the legacy interface of a member device on behalf
> of the legacy member device driver.
> 
> For example, with the SR-IOV group type, group members (VFs) can not
> present the legacy interface in an I/O BAR in BAR0 as expected by the
> legacy pci driver. If the legacy driver is running inside a virtual
> machine, the hypervisor executing the virtual machine can present a
> virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
> legacy driver accesses to this I/O BAR and forwards them to the group
> owner device (PF) using group administration commands.
> --------------------------------------------------------------------
> 
> Specifically, this driver adds support for a virtio-net VF to be exposed
> as a transitional device to a guest driver and allows the legacy IO BAR
> functionality on top.
> 
> This allows a VM which uses a legacy virtio-net driver in the guest to
> work transparently over a VF which its driver in the host is that new
> driver.
> 
> The driver can be extended easily to support some other types of virtio
> devices (e.g virtio-blk), by adding in a few places the specific type
> properties as was done for virtio-net.
> 
> For now, only the virtio-net use case was tested and as such we introduce
> the support only for such a device.
> 
> Practically,
> Upon probing a VF for a virtio-net device, in case its PF supports
> legacy access over the virtio admin commands and the VF doesn't have
BAR
> 0, we set some specific 'vfio_device_ops' to be able to simulate in
SW a
> transitional device with I/O BAR in BAR 0.
> 
> The existence of the simulated I/O bar is reported later on by
> overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
> exposes itself as a transitional device by overwriting some properties
> upon reading its config space.
> 
> Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
> guest may use it via read/write calls according to the virtio
> specification.
> 
> Any read/write towards the control parts of the BAR will be captured by
> the new driver and will be translated into admin commands towards the
> device.
> 
> Any data path read/write access (i.e. virtio driver notifications) will
> be forwarded to the physical BAR which its properties were supplied by
> the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.
> 
> With that code in place a legacy driver in the guest has the look and
> feel as if having a transitional device with legacy support for both its
> control and data path flows.
Why do we need to enable a "legacy" driver in the guest?  The very
name
suggests there's an alternative driver that perhaps doesn't require
this I/O BAR.  Why don't we just require the non-legacy driver in the
guest rather than increase our maintenance burden?  Thanks,

Alex
> 
> [1]
>
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c
> 
> Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
> ---
>  MAINTAINERS                      |   6 +
>  drivers/vfio/pci/Kconfig         |   2 +
>  drivers/vfio/pci/Makefile        |   2 +
>  drivers/vfio/pci/virtio/Kconfig  |  15 +
>  drivers/vfio/pci/virtio/Makefile |   4 +
>  drivers/vfio/pci/virtio/cmd.c    |   4 +-
>  drivers/vfio/pci/virtio/cmd.h    |   8 +
>  drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
>  8 files changed, 585 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/vfio/pci/virtio/Kconfig
>  create mode 100644 drivers/vfio/pci/virtio/Makefile
>  create mode 100644 drivers/vfio/pci/virtio/main.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bf0f54c24f81..5098418c8389 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
>  S:	Maintained
>  F:	drivers/vfio/pci/mlx5/
>  
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <yishaih at nvidia.com>
> +L:	kvm at vger.kernel.org
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>  VFIO PCI DEVICE SPECIFIC DRIVERS
>  R:	Jason Gunthorpe <jgg at nvidia.com>
>  R:	Yishai Hadas <yishaih at nvidia.com>
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 8125e5f37832..18c397df566d 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
>  
>  source "drivers/vfio/pci/pds/Kconfig"
>  
> +source "drivers/vfio/pci/virtio/Kconfig"
> +
>  endmenu
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index 45167be462d8..046139a4eca5 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
>  obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
>  
>  obj-$(CONFIG_PDS_VFIO_PCI) += pds/
> +
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
> diff --git a/drivers/vfio/pci/virtio/Kconfig
b/drivers/vfio/pci/virtio/Kconfig
> new file mode 100644
> index 000000000000..89eddce8b1bd
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VIRTIO_VFIO_PCI
> +        tristate "VFIO support for VIRTIO PCI devices"
> +        depends on VIRTIO_PCI
> +        select VFIO_PCI_CORE
> +        help
> +          This provides support for exposing VIRTIO VF devices using the
VFIO
> +          framework that can work with a legacy virtio driver in the
guest.
> +          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs
shall
> +          not indicate I/O Space.
> +          As of that this driver emulated I/O BAR in software to let a VF
be
> +          seen as a transitional device in the guest and let it work with
> +          a legacy driver.
> +
> +          If you don't know what to do here, say N.
> diff --git a/drivers/vfio/pci/virtio/Makefile
b/drivers/vfio/pci/virtio/Makefile
> new file mode 100644
> index 000000000000..584372648a03
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
> +virtio-vfio-pci-y := main.o cmd.o
> +
> diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
> index f068239cdbb0..aea9d25fbf1d 100644
> --- a/drivers/vfio/pci/virtio/cmd.c
> +++ b/drivers/vfio/pci/virtio/cmd.c
> @@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_write *in;
> +	struct virtio_admin_cmd_legacy_wr_data *in;
>  	struct scatterlist in_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> @@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_read *in;
> +	struct virtio_admin_cmd_legacy_rd_data *in;
>  	struct scatterlist in_sg, out_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
> index c2a3645f4b90..347b1dc85570 100644
> --- a/drivers/vfio/pci/virtio/cmd.h
> +++ b/drivers/vfio/pci/virtio/cmd.h
> @@ -13,7 +13,15 @@
>  
>  struct virtiovf_pci_core_device {
>  	struct vfio_pci_core_device core_device;
> +	u8 bar0_virtual_buf_size;
> +	u8 *bar0_virtual_buf;
> +	/* synchronize access to the virtual buf */
> +	struct mutex bar_mutex;
>  	int vf_id;
> +	void __iomem *notify_addr;
> +	u32 notify_offset;
> +	u8 notify_bar;
> +	u8 pci_cmd_io :1;
>  };
>  
>  int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
> diff --git a/drivers/vfio/pci/virtio/main.c
b/drivers/vfio/pci/virtio/main.c
> new file mode 100644
> index 000000000000..2486991c49f3
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/main.c
> @@ -0,0 +1,546 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights
reserved
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pci.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/types.h>
> +#include <linux/uaccess.h>
> +#include <linux/vfio.h>
> +#include <linux/vfio_pci_core.h>
> +#include <linux/virtio_pci.h>
> +#include <linux/virtio_net.h>
> +#include <linux/virtio_pci_modern.h>
> +
> +#include "cmd.h"
> +
> +#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
> +#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
> +
> +static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device
*virtvdev,
> +				 loff_t pos, char __user *buf,
> +				 size_t count, bool read)
> +{
> +	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
> +	u16 opcode;
> +	int ret;
> +
> +	mutex_lock(&virtvdev->bar_mutex);
> +	if (read) {
> +		opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
> +		ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
> +					   count, bar0_buf + pos);
> +		if (ret)
> +			goto out;
> +		if (copy_to_user(buf, bar0_buf + pos, count))
> +			ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (copy_from_user(bar0_buf + pos, buf, count)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;
> +	ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
> +				    bar0_buf + pos);
> +out:
> +	mutex_unlock(&virtvdev->bar_mutex);
> +	return ret;
> +}
> +
> +static int
> +translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
> +			    loff_t pos, char __user *buf,
> +			    size_t count, bool read)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	u16 queue_notify;
> +	int ret;
> +
> +	if (pos + count > virtvdev->bar0_virtual_buf_size)
> +		return -EINVAL;
> +
> +	switch (pos) {
> +	case VIRTIO_PCI_QUEUE_NOTIFY:
> +		if (count != sizeof(queue_notify))
> +			return -EINVAL;
> +		if (read) {
> +			ret = vfio_pci_ioread16(core_device, true, &queue_notify,
> +						virtvdev->notify_addr);
> +			if (ret)
> +				return ret;
> +			if (copy_to_user(buf, &queue_notify,
> +					 sizeof(queue_notify)))
> +				return -EFAULT;
> +			break;
> +		}
> +
> +		if (copy_from_user(&queue_notify, buf, count))
> +			return -EFAULT;
> +
> +		ret = vfio_pci_iowrite16(core_device, true, queue_notify,
> +					 virtvdev->notify_addr);
> +		break;
> +	default:
> +		ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
> +	}
> +
> +	return ret ? ret : count;
> +}
> +
> +static bool range_contains_range(loff_t range1_start, size_t count1,
> +				 loff_t range2_start, size_t count2,
> +				 loff_t *start_offset)
> +{
> +	if (range1_start <= range2_start &&
> +	    range1_start + count1 >= range2_start + count2) {
> +		*start_offset = range2_start - range1_start;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
> +					char __user *buf, size_t count,
> +					loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	loff_t copy_offset;
> +	__le32 val32;
> +	__le16 val16;
> +	u8 val8;
> +	int ret;
> +
> +	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		val16 = cpu_to_le16(0x1000);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (virtvdev->pci_cmd_io &&
> +	    range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
> +				 &copy_offset)) {
> +		if (copy_from_user(&val16, buf, sizeof(val16)))
> +			return -EFAULT;
> +		val16 |= cpu_to_le16(PCI_COMMAND_IO);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
> +				 &copy_offset)) {
> +		/* Transional needs to have revision 0 */
> +		val8 = 0;
> +		if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
> +				 &copy_offset)) {
> +		val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
> +		if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		/* Transitional devices use the PCI subsystem device id as
> +		 * virtio device id, same as legacy driver always did.
> +		 */
> +		val16 = cpu_to_le16(VIRTIO_ID_NET);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	return count;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
> +		       size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
> +		return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_read(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n",
> +				     ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user
*buf,
> +			size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
> +		loff_t copy_offset;
> +		u16 cmd;
> +
> +		if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
> +					 &copy_offset)) {
> +			if (copy_from_user(&cmd, buf + copy_offset, sizeof(cmd)))
> +				return -EFAULT;
> +			virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
> +		}
> +	}
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_write(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf,
count, false);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static int
> +virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> +				   unsigned int cmd, unsigned long arg)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
> +	void __user *uarg = (void __user *)arg;
> +	struct vfio_region_info info = {};
> +
> +	if (copy_from_user(&info, uarg, minsz))
> +		return -EFAULT;
> +
> +	if (info.argsz < minsz)
> +		return -EINVAL;
> +
> +	switch (info.index) {
> +	case VFIO_PCI_BAR0_REGION_INDEX:
> +		info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
> +		info.size = virtvdev->bar0_virtual_buf_size;
> +		info.flags = VFIO_REGION_INFO_FLAG_READ |
> +			     VFIO_REGION_INFO_FLAG_WRITE;
> +		return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static long
> +virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int
cmd,
> +			     unsigned long arg)
> +{
> +	switch (cmd) {
> +	case VFIO_DEVICE_GET_REGION_INFO:
> +		return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static int
> +virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	int ret;
> +
> +	/* Setup the BAR where the 'notify' exists to be used by vfio as
well
> +	 * This will let us mmap it only once and use it when needed.
> +	 */
> +	ret = vfio_pci_core_setup_barmap(core_device,
> +					 virtvdev->notify_bar);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_addr =
core_device->barmap[virtvdev->notify_bar] +
> +			virtvdev->notify_offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct vfio_pci_core_device *vdev = &virtvdev->core_device;
> +	int ret;
> +
> +	ret = vfio_pci_core_enable(vdev);
> +	if (ret)
> +		return ret;
> +
> +	if (virtvdev->bar0_virtual_buf) {
> +		/* upon close_device() the vfio_pci_core_disable() is called
> +		 * and will close all the previous mmaps, so it seems that the
> +		 * valid life cycle for the 'notify' addr is per open/close.
> +		 */
> +		ret = virtiovf_set_notify_addr(virtvdev);
> +		if (ret) {
> +			vfio_pci_core_disable(vdev);
> +			return ret;
> +		}
> +	}
> +
> +	vfio_pci_core_finish_enable(vdev);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
> +{
> +	vfio_pci_core_close_device(core_vdev);
> +}
> +
> +static int virtiovf_get_device_config_size(unsigned short device)
> +{
> +	switch (device) {
> +	case 0x1041:
> +		/* network card */
> +		return offsetofend(struct virtio_net_config, status);
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int virtiovf_read_notify_info(struct virtiovf_pci_core_device
*virtvdev)
> +{
> +	u64 offset;
> +	int ret;
> +	u8 bar;
> +
> +	ret = virtiovf_cmd_lq_read_notify(virtvdev,
> +				VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
> +				&bar, &offset);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_bar = bar;
> +	virtvdev->notify_offset = offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	ret = vfio_pci_core_init_dev(core_vdev);
> +	if (ret)
> +		return ret;
> +
> +	pdev = virtvdev->core_device.pdev;
> +	virtvdev->vf_id = pci_iov_vf_id(pdev);
> +	if (virtvdev->vf_id < 0)
> +		return -EINVAL;
> +
> +	ret = virtiovf_read_notify_info(virtvdev);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
> +		VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
> +		virtiovf_get_device_config_size(pdev->device);
> +	virtvdev->bar0_virtual_buf =
kzalloc(virtvdev->bar0_virtual_buf_size,
> +					     GFP_KERNEL);
> +	if (!virtvdev->bar0_virtual_buf)
> +		return -ENOMEM;
> +	mutex_init(&virtvdev->bar_mutex);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +
> +	kfree(virtvdev->bar0_virtual_buf);
> +	vfio_pci_core_release_dev(core_vdev);
> +}
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
> +	.name = "virtio-transitional-vfio-pci",
> +	.init = virtiovf_pci_init_device,
> +	.release = virtiovf_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = virtiovf_vfio_pci_core_ioctl,
> +	.read = virtiovf_pci_core_read,
> +	.write = virtiovf_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
> +	.name = "virtio-acc-vfio-pci",
> +	.init = vfio_pci_core_init_dev,
> +	.release = vfio_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = vfio_pci_core_ioctl,
> +	.device_feature = vfio_pci_core_ioctl_feature,
> +	.read = vfio_pci_core_read,
> +	.write = vfio_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static bool virtiovf_bar0_exists(struct pci_dev *pdev)
> +{
> +	struct resource *res = pdev->resource;
> +
> +	return res->flags ? true : false;
> +}
> +
> +#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
> +	(BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
> +
> +static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
> +{
> +	int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
> +	u8 *buf;
> +	int ret;
> +
> +	/* Only virtio-net is supported/tested so far */
> +	if (pdev->device != 0x1041)
> +		return false;
> +
> +	buf = kzalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return false;
> +
> +	ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
> +	if (ret)
> +		goto end;
> +
> +	if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP)
!> +		VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
> +		ret = -EOPNOTSUPP;
> +		goto end;
> +	}
> +
> +	/* confirm the used commands */
> +	memset(buf, 0, buf_size);
> +	*(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
> +	ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
> +
> +end:
> +	kfree(buf);
> +	return ret ? false : true;
> +}
> +
> +static int virtiovf_pci_probe(struct pci_dev *pdev,
> +			      const struct pci_device_id *id)
> +{
> +	const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
> +	struct virtiovf_pci_core_device *virtvdev;
> +	int ret;
> +
> +	if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev)
&&
> +	    !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
> +		ops = &virtiovf_acc_vfio_pci_tran_ops;
> +
> +	virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
> +				     &pdev->dev, ops);
> +	if (IS_ERR(virtvdev))
> +		return PTR_ERR(virtvdev);
> +
> +	dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
> +	ret = vfio_pci_core_register_device(&virtvdev->core_device);
> +	if (ret)
> +		goto out;
> +	return 0;
> +out:
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +	return ret;
> +}
> +
> +static void virtiovf_pci_remove(struct pci_dev *pdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev =
dev_get_drvdata(&pdev->dev);
> +
> +	vfio_pci_core_unregister_device(&virtvdev->core_device);
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +}
> +
> +static const struct pci_device_id virtiovf_pci_table[] = {
> +	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET,
PCI_ANY_ID) },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
> +
> +static struct pci_driver virtiovf_pci_driver = {
> +	.name = KBUILD_MODNAME,
> +	.id_table = virtiovf_pci_table,
> +	.probe = virtiovf_pci_probe,
> +	.remove = virtiovf_pci_remove,
> +	.err_handler = &vfio_pci_core_err_handlers,
> +	.driver_managed_dma = true,
> +};
> +
> +module_pci_driver(virtiovf_pci_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Yishai Hadas <yishaih at nvidia.com>");
> +MODULE_DESCRIPTION(
> +	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device
family");

On Thu, 21 Sep 2023 15:40:40 +0300
Yishai Hadas <yishaih at nvidia.com> wrote:
> Introduce a vfio driver over virtio devices to support the legacy
> interface functionality for VFs.
> 
> Background, from the virtio spec [1].
> --------------------------------------------------------------------
> In some systems, there is a need to support a virtio legacy driver with
> a device that does not directly support the legacy interface. In such
> scenarios, a group owner device can provide the legacy interface
> functionality for the group member devices. The driver of the owner
> device can then access the legacy interface of a member device on behalf
> of the legacy member device driver.
> 
> For example, with the SR-IOV group type, group members (VFs) can not
> present the legacy interface in an I/O BAR in BAR0 as expected by the
> legacy pci driver. If the legacy driver is running inside a virtual
> machine, the hypervisor executing the virtual machine can present a
> virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
> legacy driver accesses to this I/O BAR and forwards them to the group
> owner device (PF) using group administration commands.
> --------------------------------------------------------------------
> 
> Specifically, this driver adds support for a virtio-net VF to be exposed
> as a transitional device to a guest driver and allows the legacy IO BAR
> functionality on top.
> 
> This allows a VM which uses a legacy virtio-net driver in the guest to
> work transparently over a VF which its driver in the host is that new
> driver.
> 
> The driver can be extended easily to support some other types of virtio
> devices (e.g virtio-blk), by adding in a few places the specific type
> properties as was done for virtio-net.
> 
> For now, only the virtio-net use case was tested and as such we introduce
> the support only for such a device.
> 
> Practically,
> Upon probing a VF for a virtio-net device, in case its PF supports
> legacy access over the virtio admin commands and the VF doesn't have
BAR
> 0, we set some specific 'vfio_device_ops' to be able to simulate in
SW a
> transitional device with I/O BAR in BAR 0.
> 
> The existence of the simulated I/O bar is reported later on by
> overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
> exposes itself as a transitional device by overwriting some properties
> upon reading its config space.
> 
> Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
> guest may use it via read/write calls according to the virtio
> specification.
> 
> Any read/write towards the control parts of the BAR will be captured by
> the new driver and will be translated into admin commands towards the
> device.
> 
> Any data path read/write access (i.e. virtio driver notifications) will
> be forwarded to the physical BAR which its properties were supplied by
> the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.
> 
> With that code in place a legacy driver in the guest has the look and
> feel as if having a transitional device with legacy support for both its
> control and data path flows.
> 
> [1]
>
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c
> 
> Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
> ---
>  MAINTAINERS                      |   6 +
>  drivers/vfio/pci/Kconfig         |   2 +
>  drivers/vfio/pci/Makefile        |   2 +
>  drivers/vfio/pci/virtio/Kconfig  |  15 +
>  drivers/vfio/pci/virtio/Makefile |   4 +
>  drivers/vfio/pci/virtio/cmd.c    |   4 +-
>  drivers/vfio/pci/virtio/cmd.h    |   8 +
>  drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
>  8 files changed, 585 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/vfio/pci/virtio/Kconfig
>  create mode 100644 drivers/vfio/pci/virtio/Makefile
>  create mode 100644 drivers/vfio/pci/virtio/main.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bf0f54c24f81..5098418c8389 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
>  S:	Maintained
>  F:	drivers/vfio/pci/mlx5/
>  
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <yishaih at nvidia.com>
> +L:	kvm at vger.kernel.org
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>  VFIO PCI DEVICE SPECIFIC DRIVERS
>  R:	Jason Gunthorpe <jgg at nvidia.com>
>  R:	Yishai Hadas <yishaih at nvidia.com>
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 8125e5f37832..18c397df566d 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
>  
>  source "drivers/vfio/pci/pds/Kconfig"
>  
> +source "drivers/vfio/pci/virtio/Kconfig"
> +
>  endmenu
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index 45167be462d8..046139a4eca5 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
>  obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
>  
>  obj-$(CONFIG_PDS_VFIO_PCI) += pds/
> +
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
> diff --git a/drivers/vfio/pci/virtio/Kconfig
b/drivers/vfio/pci/virtio/Kconfig
> new file mode 100644
> index 000000000000..89eddce8b1bd
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VIRTIO_VFIO_PCI
> +        tristate "VFIO support for VIRTIO PCI devices"
> +        depends on VIRTIO_PCI
> +        select VFIO_PCI_CORE
> +        help
> +          This provides support for exposing VIRTIO VF devices using the
VFIO
> +          framework that can work with a legacy virtio driver in the
guest.
> +          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs
shall
> +          not indicate I/O Space.
> +          As of that this driver emulated I/O BAR in software to let a VF
be
> +          seen as a transitional device in the guest and let it work with
> +          a legacy driver.
> +
> +          If you don't know what to do here, say N.
> diff --git a/drivers/vfio/pci/virtio/Makefile
b/drivers/vfio/pci/virtio/Makefile
> new file mode 100644
> index 000000000000..584372648a03
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
> +virtio-vfio-pci-y := main.o cmd.o
> +
> diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
> index f068239cdbb0..aea9d25fbf1d 100644
> --- a/drivers/vfio/pci/virtio/cmd.c
> +++ b/drivers/vfio/pci/virtio/cmd.c
> @@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_write *in;
> +	struct virtio_admin_cmd_legacy_wr_data *in;
>  	struct scatterlist in_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> @@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_read *in;
> +	struct virtio_admin_cmd_legacy_rd_data *in;
>  	struct scatterlist in_sg, out_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
> index c2a3645f4b90..347b1dc85570 100644
> --- a/drivers/vfio/pci/virtio/cmd.h
> +++ b/drivers/vfio/pci/virtio/cmd.h
> @@ -13,7 +13,15 @@
>  
>  struct virtiovf_pci_core_device {
>  	struct vfio_pci_core_device core_device;
> +	u8 bar0_virtual_buf_size;
> +	u8 *bar0_virtual_buf;
> +	/* synchronize access to the virtual buf */
> +	struct mutex bar_mutex;
>  	int vf_id;
> +	void __iomem *notify_addr;
> +	u32 notify_offset;
> +	u8 notify_bar;
> +	u8 pci_cmd_io :1;
>  };
>  
>  int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
> diff --git a/drivers/vfio/pci/virtio/main.c
b/drivers/vfio/pci/virtio/main.c
> new file mode 100644
> index 000000000000..2486991c49f3
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/main.c
> @@ -0,0 +1,546 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights
reserved
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pci.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/types.h>
> +#include <linux/uaccess.h>
> +#include <linux/vfio.h>
> +#include <linux/vfio_pci_core.h>
> +#include <linux/virtio_pci.h>
> +#include <linux/virtio_net.h>
> +#include <linux/virtio_pci_modern.h>
> +
> +#include "cmd.h"
> +
> +#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
> +#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
> +
> +static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device
*virtvdev,
> +				 loff_t pos, char __user *buf,
> +				 size_t count, bool read)
> +{
> +	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
> +	u16 opcode;
> +	int ret;
> +
> +	mutex_lock(&virtvdev->bar_mutex);
> +	if (read) {
> +		opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
> +		ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
> +					   count, bar0_buf + pos);
> +		if (ret)
> +			goto out;
> +		if (copy_to_user(buf, bar0_buf + pos, count))
> +			ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (copy_from_user(bar0_buf + pos, buf, count)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;
> +	ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
> +				    bar0_buf + pos);
> +out:
> +	mutex_unlock(&virtvdev->bar_mutex);
> +	return ret;
> +}
> +
> +static int
> +translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
> +			    loff_t pos, char __user *buf,
> +			    size_t count, bool read)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	u16 queue_notify;
> +	int ret;
> +
> +	if (pos + count > virtvdev->bar0_virtual_buf_size)
> +		return -EINVAL;
> +
> +	switch (pos) {
> +	case VIRTIO_PCI_QUEUE_NOTIFY:
> +		if (count != sizeof(queue_notify))
> +			return -EINVAL;
> +		if (read) {
> +			ret = vfio_pci_ioread16(core_device, true, &queue_notify,
> +						virtvdev->notify_addr);
> +			if (ret)
> +				return ret;
> +			if (copy_to_user(buf, &queue_notify,
> +					 sizeof(queue_notify)))
> +				return -EFAULT;
> +			break;
> +		}
> +
> +		if (copy_from_user(&queue_notify, buf, count))
> +			return -EFAULT;
> +
> +		ret = vfio_pci_iowrite16(core_device, true, queue_notify,
> +					 virtvdev->notify_addr);
> +		break;
> +	default:
> +		ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
> +	}
> +
> +	return ret ? ret : count;
> +}
> +
> +static bool range_contains_range(loff_t range1_start, size_t count1,
> +				 loff_t range2_start, size_t count2,
> +				 loff_t *start_offset)
> +{
> +	if (range1_start <= range2_start &&
> +	    range1_start + count1 >= range2_start + count2) {
> +		*start_offset = range2_start - range1_start;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
> +					char __user *buf, size_t count,
> +					loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	loff_t copy_offset;
> +	__le32 val32;
> +	__le16 val16;
> +	u8 val8;
> +	int ret;
> +
> +	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		val16 = cpu_to_le16(0x1000);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
So we take a 0x1041 ("Virtio 1.0 network device") and turn it into a
0x1000 ("Virtio network device").  Are there no features implied by
the
device ID?  NB, a byte-wise access would read the real device ID.
> +
> +	if (virtvdev->pci_cmd_io &&
> +	    range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
> +				 &copy_offset)) {
> +		if (copy_from_user(&val16, buf, sizeof(val16)))
> +			return -EFAULT;
> +		val16 |= cpu_to_le16(PCI_COMMAND_IO);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
So we can't turn off I/O memory.
> +
> +	if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
> +				 &copy_offset)) {
> +		/* Transional needs to have revision 0 */
> +		val8 = 0;
> +		if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
> +			return -EFAULT;
> +	}
Surely some driver cares about this, right?  How is this supposed to
work in a world where libvirt parses modules.alias and automatically
loads this driver rather than vfio-pci for all 0x1041 devices?  We'd
need to denylist this driver to ever see the device for what it is.
> +
> +	if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
> +				 &copy_offset)) {
> +		val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
> +		if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
> +			return -EFAULT;
> +	}
Sloppy BAR emulation compared to the real BARs.  QEMU obviously doesn't
care.
> +
> +	if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		/* Transitional devices use the PCI subsystem device id as
> +		 * virtio device id, same as legacy driver always did.
> +		 */
Non-networking multi-line comment style throughout please.
> +		val16 = cpu_to_le16(VIRTIO_ID_NET);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	return count;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
> +		       size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
> +		return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_read(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n",
> +				     ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
If the heart of this driver is simply pretending to have an I/O BAR
where I/O accesses into that BAR are translated to accesses in the MMIO
BAR, why can't this be done in the VMM, ie. QEMU?  Could I/O to MMIO
translation in QEMU improve performance (ex. if the MMIO is mmap'd and
can be accessed without bouncing back into kernel code)?

> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user
*buf,
> +			size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
> +		loff_t copy_offset;
> +		u16 cmd;
> +
> +		if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
> +					 &copy_offset)) {
> +			if (copy_from_user(&cmd, buf + copy_offset, sizeof(cmd)))
> +				return -EFAULT;
> +			virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
If we're tracking writes to PCI_COMMAND_IO, why did we statically
report I/O enabled in the read function previously?
> +		}
> +	}
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_write(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf,
count, false);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static int
> +virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> +				   unsigned int cmd, unsigned long arg)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
> +	void __user *uarg = (void __user *)arg;
> +	struct vfio_region_info info = {};
> +
> +	if (copy_from_user(&info, uarg, minsz))
> +		return -EFAULT;
> +
> +	if (info.argsz < minsz)
> +		return -EINVAL;
> +
> +	switch (info.index) {
> +	case VFIO_PCI_BAR0_REGION_INDEX:
> +		info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
> +		info.size = virtvdev->bar0_virtual_buf_size;
> +		info.flags = VFIO_REGION_INFO_FLAG_READ |
> +			     VFIO_REGION_INFO_FLAG_WRITE;
> +		return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static long
> +virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int
cmd,
> +			     unsigned long arg)
> +{
> +	switch (cmd) {
> +	case VFIO_DEVICE_GET_REGION_INFO:
> +		return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static int
> +virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	int ret;
> +
> +	/* Setup the BAR where the 'notify' exists to be used by vfio as
well
> +	 * This will let us mmap it only once and use it when needed.
> +	 */
> +	ret = vfio_pci_core_setup_barmap(core_device,
> +					 virtvdev->notify_bar);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_addr =
core_device->barmap[virtvdev->notify_bar] +
> +			virtvdev->notify_offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct vfio_pci_core_device *vdev = &virtvdev->core_device;
> +	int ret;
> +
> +	ret = vfio_pci_core_enable(vdev);
> +	if (ret)
> +		return ret;
> +
> +	if (virtvdev->bar0_virtual_buf) {
> +		/* upon close_device() the vfio_pci_core_disable() is called
> +		 * and will close all the previous mmaps, so it seems that the
> +		 * valid life cycle for the 'notify' addr is per open/close.
> +		 */
> +		ret = virtiovf_set_notify_addr(virtvdev);
> +		if (ret) {
> +			vfio_pci_core_disable(vdev);
> +			return ret;
> +		}
> +	}
> +
> +	vfio_pci_core_finish_enable(vdev);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
> +{
> +	vfio_pci_core_close_device(core_vdev);
> +}
Why does this function exist?
> +
> +static int virtiovf_get_device_config_size(unsigned short device)
> +{
> +	switch (device) {
> +	case 0x1041:
> +		/* network card */
> +		return offsetofend(struct virtio_net_config, status);
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int virtiovf_read_notify_info(struct virtiovf_pci_core_device
*virtvdev)
> +{
> +	u64 offset;
> +	int ret;
> +	u8 bar;
> +
> +	ret = virtiovf_cmd_lq_read_notify(virtvdev,
> +				VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
> +				&bar, &offset);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_bar = bar;
> +	virtvdev->notify_offset = offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	ret = vfio_pci_core_init_dev(core_vdev);
> +	if (ret)
> +		return ret;
> +
> +	pdev = virtvdev->core_device.pdev;
> +	virtvdev->vf_id = pci_iov_vf_id(pdev);
> +	if (virtvdev->vf_id < 0)
> +		return -EINVAL;
vf_id is never used.
> +
> +	ret = virtiovf_read_notify_info(virtvdev);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
> +		VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
> +		virtiovf_get_device_config_size(pdev->device);
> +	virtvdev->bar0_virtual_buf =
kzalloc(virtvdev->bar0_virtual_buf_size,
> +					     GFP_KERNEL);
> +	if (!virtvdev->bar0_virtual_buf)
> +		return -ENOMEM;
> +	mutex_init(&virtvdev->bar_mutex);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +
> +	kfree(virtvdev->bar0_virtual_buf);
> +	vfio_pci_core_release_dev(core_vdev);
> +}
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
> +	.name = "virtio-transitional-vfio-pci",
> +	.init = virtiovf_pci_init_device,
> +	.release = virtiovf_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = virtiovf_vfio_pci_core_ioctl,
> +	.read = virtiovf_pci_core_read,
> +	.write = virtiovf_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
> +	.name = "virtio-acc-vfio-pci",
> +	.init = vfio_pci_core_init_dev,
> +	.release = vfio_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = vfio_pci_core_ioctl,
> +	.device_feature = vfio_pci_core_ioctl_feature,
> +	.read = vfio_pci_core_read,
> +	.write = vfio_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
Why are we claiming devices that should just use vfio-pci instead?
> +
> +static bool virtiovf_bar0_exists(struct pci_dev *pdev)
> +{
> +	struct resource *res = pdev->resource;
> +
> +	return res->flags ? true : false;
> +}
> +
> +#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
> +	(BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
> +
> +static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
> +{
> +	int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
> +	u8 *buf;
> +	int ret;
> +
> +	/* Only virtio-net is supported/tested so far */
> +	if (pdev->device != 0x1041)
> +		return false;
Seems like the ID table should handle this, why are we preemptively
claiming all virtio devices... or actually all 0x1af4 devices, which
might not even be virtio, ex. the non-virtio ivshmem devices is 0x1110.
> +
> +	buf = kzalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return false;
> +
> +	ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
> +	if (ret)
> +		goto end;
> +
> +	if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP)
!> +		VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
> +		ret = -EOPNOTSUPP;
> +		goto end;
> +	}
> +
> +	/* confirm the used commands */
> +	memset(buf, 0, buf_size);
> +	*(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
> +	ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
> +
> +end:
> +	kfree(buf);
> +	return ret ? false : true;
> +}
> +
> +static int virtiovf_pci_probe(struct pci_dev *pdev,
> +			      const struct pci_device_id *id)
> +{
> +	const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
> +	struct virtiovf_pci_core_device *virtvdev;
> +	int ret;
> +
> +	if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev)
&&
> +	    !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
> +		ops = &virtiovf_acc_vfio_pci_tran_ops;
> +
> +	virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
> +				     &pdev->dev, ops);
> +	if (IS_ERR(virtvdev))
> +		return PTR_ERR(virtvdev);
> +
> +	dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
> +	ret = vfio_pci_core_register_device(&virtvdev->core_device);
> +	if (ret)
> +		goto out;
> +	return 0;
> +out:
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +	return ret;
> +}
> +
> +static void virtiovf_pci_remove(struct pci_dev *pdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev =
dev_get_drvdata(&pdev->dev);
> +
> +	vfio_pci_core_unregister_device(&virtvdev->core_device);
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +}
> +
> +static const struct pci_device_id virtiovf_pci_table[] = {
> +	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET,
PCI_ANY_ID) },
libvirt will blindly use this driver for all devices matching this as
we've discussed how it should make use of modules.alias.  I don't think
this driver should be squatting on devices where it doesn't add value
and it's not clear whether this is adding or subtracting value in all
cases for the one NIC that it modifies.  How should libvirt choose when
and where to use this driver?  What regressions are we going to see
with VMs that previously saw "modern" virtio-net devices and now see a
legacy compatible device?  Thanks,

Alex
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
> +
> +static struct pci_driver virtiovf_pci_driver = {
> +	.name = KBUILD_MODNAME,
> +	.id_table = virtiovf_pci_table,
> +	.probe = virtiovf_pci_probe,
> +	.remove = virtiovf_pci_remove,
> +	.err_handler = &vfio_pci_core_err_handlers,
> +	.driver_managed_dma = true,
> +};
> +
> +module_pci_driver(virtiovf_pci_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Yishai Hadas <yishaih at nvidia.com>");
> +MODULE_DESCRIPTION(
> +	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device
family");

On Thu, Sep 21, 2023 at 03:40:40PM +0300, Yishai Hadas
wrote:
> Introduce a vfio driver over virtio devices to support the legacy
> interface functionality for VFs.
> 
> Background, from the virtio spec [1].
> --------------------------------------------------------------------
> In some systems, there is a need to support a virtio legacy driver with
> a device that does not directly support the legacy interface. In such
> scenarios, a group owner device can provide the legacy interface
> functionality for the group member devices. The driver of the owner
> device can then access the legacy interface of a member device on behalf
> of the legacy member device driver.
> 
> For example, with the SR-IOV group type, group members (VFs) can not
> present the legacy interface in an I/O BAR in BAR0 as expected by the
> legacy pci driver. If the legacy driver is running inside a virtual
> machine, the hypervisor executing the virtual machine can present a
> virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
> legacy driver accesses to this I/O BAR and forwards them to the group
> owner device (PF) using group administration commands.
> --------------------------------------------------------------------
> 
> Specifically, this driver adds support for a virtio-net VF to be exposed
> as a transitional device to a guest driver and allows the legacy IO BAR
> functionality on top.
> 
> This allows a VM which uses a legacy virtio-net driver in the guest to
> work transparently over a VF which its driver in the host is that new
> driver.
> 
> The driver can be extended easily to support some other types of virtio
> devices (e.g virtio-blk), by adding in a few places the specific type
> properties as was done for virtio-net.
> 
> For now, only the virtio-net use case was tested and as such we introduce
> the support only for such a device.
> 
> Practically,
> Upon probing a VF for a virtio-net device, in case its PF supports
> legacy access over the virtio admin commands and the VF doesn't have
BAR
> 0, we set some specific 'vfio_device_ops' to be able to simulate in
SW a
> transitional device with I/O BAR in BAR 0.
> 
> The existence of the simulated I/O bar is reported later on by
> overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
> exposes itself as a transitional device by overwriting some properties
> upon reading its config space.
> 
> Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
> guest may use it via read/write calls according to the virtio
> specification.
> 
> Any read/write towards the control parts of the BAR will be captured by
> the new driver and will be translated into admin commands towards the
> device.
> 
> Any data path read/write access (i.e. virtio driver notifications) will
> be forwarded to the physical BAR which its properties were supplied by
> the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.
> 
> With that code in place a legacy driver in the guest has the look and
> feel as if having a transitional device with legacy support for both its
> control and data path flows.
> 
> [1]
>
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c
> 
> Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
> ---
>  MAINTAINERS                      |   6 +
>  drivers/vfio/pci/Kconfig         |   2 +
>  drivers/vfio/pci/Makefile        |   2 +
>  drivers/vfio/pci/virtio/Kconfig  |  15 +
>  drivers/vfio/pci/virtio/Makefile |   4 +
>  drivers/vfio/pci/virtio/cmd.c    |   4 +-
>  drivers/vfio/pci/virtio/cmd.h    |   8 +
>  drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
>  8 files changed, 585 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/vfio/pci/virtio/Kconfig
>  create mode 100644 drivers/vfio/pci/virtio/Makefile
>  create mode 100644 drivers/vfio/pci/virtio/main.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bf0f54c24f81..5098418c8389 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
>  S:	Maintained
>  F:	drivers/vfio/pci/mlx5/
>  
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <yishaih at nvidia.com>
> +L:	kvm at vger.kernel.org
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>  VFIO PCI DEVICE SPECIFIC DRIVERS
>  R:	Jason Gunthorpe <jgg at nvidia.com>
>  R:	Yishai Hadas <yishaih at nvidia.com>
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 8125e5f37832..18c397df566d 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
>  
>  source "drivers/vfio/pci/pds/Kconfig"
>  
> +source "drivers/vfio/pci/virtio/Kconfig"
> +
>  endmenu
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index 45167be462d8..046139a4eca5 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
>  obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
>  
>  obj-$(CONFIG_PDS_VFIO_PCI) += pds/
> +
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
> diff --git a/drivers/vfio/pci/virtio/Kconfig
b/drivers/vfio/pci/virtio/Kconfig
> new file mode 100644
> index 000000000000..89eddce8b1bd
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VIRTIO_VFIO_PCI
> +        tristate "VFIO support for VIRTIO PCI devices"
> +        depends on VIRTIO_PCI
> +        select VFIO_PCI_CORE
> +        help
> +          This provides support for exposing VIRTIO VF devices using the
VFIO
> +          framework that can work with a legacy virtio driver in the
guest.
> +          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs
shall
> +          not indicate I/O Space.
> +          As of that this driver emulated I/O BAR in software to let a VF
be
> +          seen as a transitional device in the guest and let it work with
> +          a legacy driver.
> +
> +          If you don't know what to do here, say N.
> diff --git a/drivers/vfio/pci/virtio/Makefile
b/drivers/vfio/pci/virtio/Makefile
> new file mode 100644
> index 000000000000..584372648a03
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
> +virtio-vfio-pci-y := main.o cmd.o
> +
> diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
> index f068239cdbb0..aea9d25fbf1d 100644
> --- a/drivers/vfio/pci/virtio/cmd.c
> +++ b/drivers/vfio/pci/virtio/cmd.c
> @@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_write *in;
> +	struct virtio_admin_cmd_legacy_wr_data *in;
>  	struct scatterlist in_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> @@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_read *in;
> +	struct virtio_admin_cmd_legacy_rd_data *in;
>  	struct scatterlist in_sg, out_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
> index c2a3645f4b90..347b1dc85570 100644
> --- a/drivers/vfio/pci/virtio/cmd.h
> +++ b/drivers/vfio/pci/virtio/cmd.h
> @@ -13,7 +13,15 @@
>  
>  struct virtiovf_pci_core_device {
>  	struct vfio_pci_core_device core_device;
> +	u8 bar0_virtual_buf_size;
> +	u8 *bar0_virtual_buf;
> +	/* synchronize access to the virtual buf */
> +	struct mutex bar_mutex;
>  	int vf_id;
> +	void __iomem *notify_addr;
> +	u32 notify_offset;
> +	u8 notify_bar;
> +	u8 pci_cmd_io :1;
>  };
>  
>  int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
> diff --git a/drivers/vfio/pci/virtio/main.c
b/drivers/vfio/pci/virtio/main.c
> new file mode 100644
> index 000000000000..2486991c49f3
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/main.c
> @@ -0,0 +1,546 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights
reserved
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pci.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/types.h>
> +#include <linux/uaccess.h>
> +#include <linux/vfio.h>
> +#include <linux/vfio_pci_core.h>
> +#include <linux/virtio_pci.h>
> +#include <linux/virtio_net.h>
> +#include <linux/virtio_pci_modern.h>
> +
> +#include "cmd.h"
> +
> +#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
> +#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
> +
> +static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device
*virtvdev,
> +				 loff_t pos, char __user *buf,
> +				 size_t count, bool read)
> +{
> +	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
> +	u16 opcode;
> +	int ret;
> +
> +	mutex_lock(&virtvdev->bar_mutex);
> +	if (read) {
> +		opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
This "true" seems wrong. You need to know whether guest wants
msix enabled for the device or not.

> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
> +		ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
> +					   count, bar0_buf + pos);
> +		if (ret)
> +			goto out;
> +		if (copy_to_user(buf, bar0_buf + pos, count))
> +			ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (copy_from_user(bar0_buf + pos, buf, count)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;

same
> +	ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
> +				    bar0_buf + pos);
> +out:
> +	mutex_unlock(&virtvdev->bar_mutex);
> +	return ret;
> +}
> +
> +static int
> +translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
> +			    loff_t pos, char __user *buf,
> +			    size_t count, bool read)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	u16 queue_notify;
> +	int ret;
> +
> +	if (pos + count > virtvdev->bar0_virtual_buf_size)
> +		return -EINVAL;
> +
> +	switch (pos) {
> +	case VIRTIO_PCI_QUEUE_NOTIFY:
> +		if (count != sizeof(queue_notify))
> +			return -EINVAL;
> +		if (read) {
> +			ret = vfio_pci_ioread16(core_device, true, &queue_notify,
> +						virtvdev->notify_addr);
> +			if (ret)
> +				return ret;
> +			if (copy_to_user(buf, &queue_notify,
> +					 sizeof(queue_notify)))
> +				return -EFAULT;
> +			break;
> +		}
> +
> +		if (copy_from_user(&queue_notify, buf, count))
> +			return -EFAULT;
> +
> +		ret = vfio_pci_iowrite16(core_device, true, queue_notify,
> +					 virtvdev->notify_addr);
> +		break;
> +	default:
> +		ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
> +	}
> +
> +	return ret ? ret : count;
> +}
> +
> +static bool range_contains_range(loff_t range1_start, size_t count1,
> +				 loff_t range2_start, size_t count2,
> +				 loff_t *start_offset)
> +{
> +	if (range1_start <= range2_start &&
> +	    range1_start + count1 >= range2_start + count2) {
> +		*start_offset = range2_start - range1_start;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
> +					char __user *buf, size_t count,
> +					loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	loff_t copy_offset;
> +	__le32 val32;
> +	__le16 val16;
> +	u8 val8;
> +	int ret;
> +
> +	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		val16 = cpu_to_le16(0x1000);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (virtvdev->pci_cmd_io &&
> +	    range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
> +				 &copy_offset)) {
> +		if (copy_from_user(&val16, buf, sizeof(val16)))
> +			return -EFAULT;
> +		val16 |= cpu_to_le16(PCI_COMMAND_IO);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
> +				 &copy_offset)) {
> +		/* Transional needs to have revision 0 */
> +		val8 = 0;
> +		if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
> +				 &copy_offset)) {
> +		val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
> +		if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		/* Transitional devices use the PCI subsystem device id as
> +		 * virtio device id, same as legacy driver always did.
> +		 */
> +		val16 = cpu_to_le16(VIRTIO_ID_NET);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	return count;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
> +		       size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
> +		return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_read(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n",
> +				     ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user
*buf,
> +			size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
> +		loff_t copy_offset;
> +		u16 cmd;
> +
> +		if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
> +					 &copy_offset)) {
> +			if (copy_from_user(&cmd, buf + copy_offset, sizeof(cmd)))
> +				return -EFAULT;
> +			virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
> +		}
> +	}
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_write(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf,
count, false);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static int
> +virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> +				   unsigned int cmd, unsigned long arg)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
> +	void __user *uarg = (void __user *)arg;
> +	struct vfio_region_info info = {};
> +
> +	if (copy_from_user(&info, uarg, minsz))
> +		return -EFAULT;
> +
> +	if (info.argsz < minsz)
> +		return -EINVAL;
> +
> +	switch (info.index) {
> +	case VFIO_PCI_BAR0_REGION_INDEX:
> +		info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
> +		info.size = virtvdev->bar0_virtual_buf_size;
> +		info.flags = VFIO_REGION_INFO_FLAG_READ |
> +			     VFIO_REGION_INFO_FLAG_WRITE;
> +		return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static long
> +virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int
cmd,
> +			     unsigned long arg)
> +{
> +	switch (cmd) {
> +	case VFIO_DEVICE_GET_REGION_INFO:
> +		return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static int
> +virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	int ret;
> +
> +	/* Setup the BAR where the 'notify' exists to be used by vfio as
well
> +	 * This will let us mmap it only once and use it when needed.
> +	 */
> +	ret = vfio_pci_core_setup_barmap(core_device,
> +					 virtvdev->notify_bar);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_addr =
core_device->barmap[virtvdev->notify_bar] +
> +			virtvdev->notify_offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct vfio_pci_core_device *vdev = &virtvdev->core_device;
> +	int ret;
> +
> +	ret = vfio_pci_core_enable(vdev);
> +	if (ret)
> +		return ret;
> +
> +	if (virtvdev->bar0_virtual_buf) {
> +		/* upon close_device() the vfio_pci_core_disable() is called
> +		 * and will close all the previous mmaps, so it seems that the
> +		 * valid life cycle for the 'notify' addr is per open/close.
> +		 */
> +		ret = virtiovf_set_notify_addr(virtvdev);
> +		if (ret) {
> +			vfio_pci_core_disable(vdev);
> +			return ret;
> +		}
> +	}
> +
> +	vfio_pci_core_finish_enable(vdev);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
> +{
> +	vfio_pci_core_close_device(core_vdev);
> +}
> +
> +static int virtiovf_get_device_config_size(unsigned short device)
> +{
> +	switch (device) {
> +	case 0x1041:
> +		/* network card */
> +		return offsetofend(struct virtio_net_config, status);
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int virtiovf_read_notify_info(struct virtiovf_pci_core_device
*virtvdev)
> +{
> +	u64 offset;
> +	int ret;
> +	u8 bar;
> +
> +	ret = virtiovf_cmd_lq_read_notify(virtvdev,
> +				VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
> +				&bar, &offset);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_bar = bar;
> +	virtvdev->notify_offset = offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	ret = vfio_pci_core_init_dev(core_vdev);
> +	if (ret)
> +		return ret;
> +
> +	pdev = virtvdev->core_device.pdev;
> +	virtvdev->vf_id = pci_iov_vf_id(pdev);
> +	if (virtvdev->vf_id < 0)
> +		return -EINVAL;
> +
> +	ret = virtiovf_read_notify_info(virtvdev);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
> +		VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
> +		virtiovf_get_device_config_size(pdev->device);
> +	virtvdev->bar0_virtual_buf =
kzalloc(virtvdev->bar0_virtual_buf_size,
> +					     GFP_KERNEL);
> +	if (!virtvdev->bar0_virtual_buf)
> +		return -ENOMEM;
> +	mutex_init(&virtvdev->bar_mutex);
> +	return 0;
> +}

There is very little vfio specific above. I feel with a bit of
refactoring the logic parts can be moved to virtio, with just
vfio things under vfio (mostly, vfio lets user disable memory or set low PM
state
so it has to be careful not to access device in such cases).
E.g.:


	virtio_legacy_translate_offset(....)
	copy_from_user(...)
	vfio_pci_iowrite16(...)

and virtio_legacy_translate_offset would live under virtio.

Something similar for config space hacks.

> +
> +static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +
> +	kfree(virtvdev->bar0_virtual_buf);
> +	vfio_pci_core_release_dev(core_vdev);
> +}
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
> +	.name = "virtio-transitional-vfio-pci",
> +	.init = virtiovf_pci_init_device,
> +	.release = virtiovf_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = virtiovf_vfio_pci_core_ioctl,
> +	.read = virtiovf_pci_core_read,
> +	.write = virtiovf_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
> +	.name = "virtio-acc-vfio-pci",
> +	.init = vfio_pci_core_init_dev,
> +	.release = vfio_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = vfio_pci_core_ioctl,
> +	.device_feature = vfio_pci_core_ioctl_feature,
> +	.read = vfio_pci_core_read,
> +	.write = vfio_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static bool virtiovf_bar0_exists(struct pci_dev *pdev)
> +{
> +	struct resource *res = pdev->resource;
> +
> +	return res->flags ? true : false;
> +}
> +
> +#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
> +	(BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
> +
> +static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
> +{
> +	int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
> +	u8 *buf;
> +	int ret;
> +
> +	/* Only virtio-net is supported/tested so far */
> +	if (pdev->device != 0x1041)
> +		return false;
> +
> +	buf = kzalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return false;
> +
> +	ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
> +	if (ret)
> +		goto end;
> +
> +	if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP)
!> +		VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
> +		ret = -EOPNOTSUPP;
> +		goto end;
> +	}
> +
> +	/* confirm the used commands */
> +	memset(buf, 0, buf_size);
> +	*(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
> +	ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
> +
> +end:
> +	kfree(buf);
> +	return ret ? false : true;
> +}

This is virtio stuff too.
> +
> +static int virtiovf_pci_probe(struct pci_dev *pdev,
> +			      const struct pci_device_id *id)
> +{
> +	const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
> +	struct virtiovf_pci_core_device *virtvdev;
> +	int ret;
> +
> +	if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev)
&&
> +	    !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
> +		ops = &virtiovf_acc_vfio_pci_tran_ops;
> +
> +	virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
> +				     &pdev->dev, ops);
> +	if (IS_ERR(virtvdev))
> +		return PTR_ERR(virtvdev);
> +
> +	dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
> +	ret = vfio_pci_core_register_device(&virtvdev->core_device);
> +	if (ret)
> +		goto out;
> +	return 0;
> +out:
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +	return ret;
> +}
> +
> +static void virtiovf_pci_remove(struct pci_dev *pdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev =
dev_get_drvdata(&pdev->dev);
> +
> +	vfio_pci_core_unregister_device(&virtvdev->core_device);
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +}
> +
> +static const struct pci_device_id virtiovf_pci_table[] = {
> +	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET,
PCI_ANY_ID) },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
> +
> +static struct pci_driver virtiovf_pci_driver = {
> +	.name = KBUILD_MODNAME,
> +	.id_table = virtiovf_pci_table,
> +	.probe = virtiovf_pci_probe,
> +	.remove = virtiovf_pci_remove,
> +	.err_handler = &vfio_pci_core_err_handlers,
> +	.driver_managed_dma = true,
> +};
> +
> +module_pci_driver(virtiovf_pci_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Yishai Hadas <yishaih at nvidia.com>");
> +MODULE_DESCRIPTION(
> +	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device
family");
> -- 
> 2.27.0

On Thu, Sep 21, 2023 at 03:40:40PM +0300, Yishai Hadas
wrote:
> Introduce a vfio driver over virtio devices to support the legacy
> interface functionality for VFs.
> 
> Background, from the virtio spec [1].
> --------------------------------------------------------------------
> In some systems, there is a need to support a virtio legacy driver with
> a device that does not directly support the legacy interface. In such
> scenarios, a group owner device can provide the legacy interface
> functionality for the group member devices. The driver of the owner
> device can then access the legacy interface of a member device on behalf
> of the legacy member device driver.
> 
> For example, with the SR-IOV group type, group members (VFs) can not
> present the legacy interface in an I/O BAR in BAR0 as expected by the
> legacy pci driver. If the legacy driver is running inside a virtual
> machine, the hypervisor executing the virtual machine can present a
> virtual device with an I/O BAR in BAR0. The hypervisor intercepts the
> legacy driver accesses to this I/O BAR and forwards them to the group
> owner device (PF) using group administration commands.
> --------------------------------------------------------------------
> 
> Specifically, this driver adds support for a virtio-net VF to be exposed
> as a transitional device to a guest driver and allows the legacy IO BAR
> functionality on top.
> 
> This allows a VM which uses a legacy virtio-net driver in the guest to
> work transparently over a VF which its driver in the host is that new
> driver.
> 
> The driver can be extended easily to support some other types of virtio
> devices (e.g virtio-blk), by adding in a few places the specific type
> properties as was done for virtio-net.
> 
> For now, only the virtio-net use case was tested and as such we introduce
> the support only for such a device.
> 
> Practically,
> Upon probing a VF for a virtio-net device, in case its PF supports
> legacy access over the virtio admin commands and the VF doesn't have
BAR
> 0, we set some specific 'vfio_device_ops' to be able to simulate in
SW a
> transitional device with I/O BAR in BAR 0.
> 
> The existence of the simulated I/O bar is reported later on by
> overwriting the VFIO_DEVICE_GET_REGION_INFO command and the device
> exposes itself as a transitional device by overwriting some properties
> upon reading its config space.
> 
> Once we report the existence of I/O BAR as BAR 0 a legacy driver in the
> guest may use it via read/write calls according to the virtio
> specification.
> 
> Any read/write towards the control parts of the BAR will be captured by
> the new driver and will be translated into admin commands towards the
> device.
> 
> Any data path read/write access (i.e. virtio driver notifications) will
> be forwarded to the physical BAR which its properties were supplied by
> the command VIRTIO_PCI_QUEUE_NOTIFY upon the probing/init flow.
> 
> With that code in place a legacy driver in the guest has the look and
> feel as if having a transitional device with legacy support for both its
> control and data path flows.
> 
> [1]
>
https://github.com/oasis-tcs/virtio-spec/commit/03c2d32e5093ca9f2a17797242fbef88efe94b8c
> 
> Signed-off-by: Yishai Hadas <yishaih at nvidia.com>
> ---
>  MAINTAINERS                      |   6 +
>  drivers/vfio/pci/Kconfig         |   2 +
>  drivers/vfio/pci/Makefile        |   2 +
>  drivers/vfio/pci/virtio/Kconfig  |  15 +
>  drivers/vfio/pci/virtio/Makefile |   4 +
>  drivers/vfio/pci/virtio/cmd.c    |   4 +-
>  drivers/vfio/pci/virtio/cmd.h    |   8 +
>  drivers/vfio/pci/virtio/main.c   | 546 +++++++++++++++++++++++++++++++
>  8 files changed, 585 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/vfio/pci/virtio/Kconfig
>  create mode 100644 drivers/vfio/pci/virtio/Makefile
>  create mode 100644 drivers/vfio/pci/virtio/main.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index bf0f54c24f81..5098418c8389 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -22624,6 +22624,12 @@ L:	kvm at vger.kernel.org
>  S:	Maintained
>  F:	drivers/vfio/pci/mlx5/
>  
> +VFIO VIRTIO PCI DRIVER
> +M:	Yishai Hadas <yishaih at nvidia.com>
> +L:	kvm at vger.kernel.org
> +S:	Maintained
> +F:	drivers/vfio/pci/virtio
> +
>  VFIO PCI DEVICE SPECIFIC DRIVERS
>  R:	Jason Gunthorpe <jgg at nvidia.com>
>  R:	Yishai Hadas <yishaih at nvidia.com>
> diff --git a/drivers/vfio/pci/Kconfig b/drivers/vfio/pci/Kconfig
> index 8125e5f37832..18c397df566d 100644
> --- a/drivers/vfio/pci/Kconfig
> +++ b/drivers/vfio/pci/Kconfig
> @@ -65,4 +65,6 @@ source "drivers/vfio/pci/hisilicon/Kconfig"
>  
>  source "drivers/vfio/pci/pds/Kconfig"
>  
> +source "drivers/vfio/pci/virtio/Kconfig"
> +
>  endmenu
> diff --git a/drivers/vfio/pci/Makefile b/drivers/vfio/pci/Makefile
> index 45167be462d8..046139a4eca5 100644
> --- a/drivers/vfio/pci/Makefile
> +++ b/drivers/vfio/pci/Makefile
> @@ -13,3 +13,5 @@ obj-$(CONFIG_MLX5_VFIO_PCI)           += mlx5/
>  obj-$(CONFIG_HISI_ACC_VFIO_PCI) += hisilicon/
>  
>  obj-$(CONFIG_PDS_VFIO_PCI) += pds/
> +
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio/
> diff --git a/drivers/vfio/pci/virtio/Kconfig
b/drivers/vfio/pci/virtio/Kconfig
> new file mode 100644
> index 000000000000..89eddce8b1bd
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +config VIRTIO_VFIO_PCI
> +        tristate "VFIO support for VIRTIO PCI devices"
> +        depends on VIRTIO_PCI
> +        select VFIO_PCI_CORE
> +        help
> +          This provides support for exposing VIRTIO VF devices using the
VFIO
> +          framework that can work with a legacy virtio driver in the
guest.
> +          Based on PCIe spec, VFs do not support I/O Space; thus, VF BARs
shall
> +          not indicate I/O Space.
> +          As of that this driver emulated I/O BAR in software to let a VF
be
> +          seen as a transitional device in the guest and let it work with
> +          a legacy driver.
> +
> +          If you don't know what to do here, say N.
> diff --git a/drivers/vfio/pci/virtio/Makefile
b/drivers/vfio/pci/virtio/Makefile
> new file mode 100644
> index 000000000000..584372648a03
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/Makefile
> @@ -0,0 +1,4 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +obj-$(CONFIG_VIRTIO_VFIO_PCI) += virtio-vfio-pci.o
> +virtio-vfio-pci-y := main.o cmd.o
> +
> diff --git a/drivers/vfio/pci/virtio/cmd.c b/drivers/vfio/pci/virtio/cmd.c
> index f068239cdbb0..aea9d25fbf1d 100644
> --- a/drivers/vfio/pci/virtio/cmd.c
> +++ b/drivers/vfio/pci/virtio/cmd.c
> @@ -44,7 +44,7 @@ int virtiovf_cmd_lr_write(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_write *in;
> +	struct virtio_admin_cmd_legacy_wr_data *in;
>  	struct scatterlist in_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> @@ -74,7 +74,7 @@ int virtiovf_cmd_lr_read(struct virtiovf_pci_core_device
*virtvdev, u16 opcode,
>  {
>  	struct virtio_device *virtio_dev >  	
virtio_pci_vf_get_pf_dev(virtvdev->core_device.pdev);
> -	struct virtio_admin_cmd_data_lr_read *in;
> +	struct virtio_admin_cmd_legacy_rd_data *in;
>  	struct scatterlist in_sg, out_sg;
>  	struct virtio_admin_cmd cmd = {};
>  	int ret;
> diff --git a/drivers/vfio/pci/virtio/cmd.h b/drivers/vfio/pci/virtio/cmd.h
> index c2a3645f4b90..347b1dc85570 100644
> --- a/drivers/vfio/pci/virtio/cmd.h
> +++ b/drivers/vfio/pci/virtio/cmd.h
> @@ -13,7 +13,15 @@
>  
>  struct virtiovf_pci_core_device {
>  	struct vfio_pci_core_device core_device;
> +	u8 bar0_virtual_buf_size;
> +	u8 *bar0_virtual_buf;
> +	/* synchronize access to the virtual buf */
> +	struct mutex bar_mutex;
>  	int vf_id;
> +	void __iomem *notify_addr;
> +	u32 notify_offset;
> +	u8 notify_bar;
> +	u8 pci_cmd_io :1;
>  };
>  
>  int virtiovf_cmd_list_query(struct pci_dev *pdev, u8 *buf, int buf_size);
> diff --git a/drivers/vfio/pci/virtio/main.c
b/drivers/vfio/pci/virtio/main.c
> new file mode 100644
> index 000000000000..2486991c49f3
> --- /dev/null
> +++ b/drivers/vfio/pci/virtio/main.c
> @@ -0,0 +1,546 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2023, NVIDIA CORPORATION & AFFILIATES. All rights
reserved
> + */
> +
> +#include <linux/device.h>
> +#include <linux/module.h>
> +#include <linux/mutex.h>
> +#include <linux/pci.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/types.h>
> +#include <linux/uaccess.h>
> +#include <linux/vfio.h>
> +#include <linux/vfio_pci_core.h>
> +#include <linux/virtio_pci.h>
> +#include <linux/virtio_net.h>
> +#include <linux/virtio_pci_modern.h>
> +
> +#include "cmd.h"
> +
> +#define VIRTIO_LEGACY_IO_BAR_HEADER_LEN 20
> +#define VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN 4
> +
> +static int virtiovf_issue_lr_cmd(struct virtiovf_pci_core_device
*virtvdev,
> +				 loff_t pos, char __user *buf,
> +				 size_t count, bool read)
> +{
> +	u8 *bar0_buf = virtvdev->bar0_virtual_buf;
> +	u16 opcode;
> +	int ret;
> +
> +	mutex_lock(&virtvdev->bar_mutex);
> +	if (read) {
> +		opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ;
> +		ret = virtiovf_cmd_lr_read(virtvdev, opcode, pos,
> +					   count, bar0_buf + pos);
> +		if (ret)
> +			goto out;
> +		if (copy_to_user(buf, bar0_buf + pos, count))
> +			ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	if (copy_from_user(bar0_buf + pos, buf, count)) {
> +		ret = -EFAULT;
> +		goto out;
> +	}
> +
> +	opcode = (pos < VIRTIO_PCI_CONFIG_OFF(true)) ?
> +			VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE :
> +			VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE;
> +	ret = virtiovf_cmd_lr_write(virtvdev, opcode, pos, count,
> +				    bar0_buf + pos);
> +out:
> +	mutex_unlock(&virtvdev->bar_mutex);
> +	return ret;
> +}
> +
> +static int
> +translate_io_bar_to_mem_bar(struct virtiovf_pci_core_device *virtvdev,
> +			    loff_t pos, char __user *buf,
> +			    size_t count, bool read)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	u16 queue_notify;
> +	int ret;
> +
> +	if (pos + count > virtvdev->bar0_virtual_buf_size)
> +		return -EINVAL;
> +
> +	switch (pos) {
> +	case VIRTIO_PCI_QUEUE_NOTIFY:
> +		if (count != sizeof(queue_notify))
> +			return -EINVAL;
> +		if (read) {
> +			ret = vfio_pci_ioread16(core_device, true, &queue_notify,
> +						virtvdev->notify_addr);
> +			if (ret)
> +				return ret;
> +			if (copy_to_user(buf, &queue_notify,
> +					 sizeof(queue_notify)))
> +				return -EFAULT;
> +			break;
> +		}
> +
> +		if (copy_from_user(&queue_notify, buf, count))
> +			return -EFAULT;
> +
> +		ret = vfio_pci_iowrite16(core_device, true, queue_notify,
> +					 virtvdev->notify_addr);
> +		break;
> +	default:
> +		ret = virtiovf_issue_lr_cmd(virtvdev, pos, buf, count, read);
> +	}
> +
> +	return ret ? ret : count;
> +}
> +
> +static bool range_contains_range(loff_t range1_start, size_t count1,
> +				 loff_t range2_start, size_t count2,
> +				 loff_t *start_offset)
> +{
> +	if (range1_start <= range2_start &&
> +	    range1_start + count1 >= range2_start + count2) {
> +		*start_offset = range2_start - range1_start;
> +		return true;
> +	}
> +	return false;
> +}
> +
> +static ssize_t virtiovf_pci_read_config(struct vfio_device *core_vdev,
> +					char __user *buf, size_t count,
> +					loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	loff_t copy_offset;
> +	__le32 val32;
> +	__le16 val16;
> +	u8 val8;
> +	int ret;
> +
> +	ret = vfio_pci_core_read(core_vdev, buf, count, ppos);
> +	if (ret < 0)
> +		return ret;
> +
> +	if (range_contains_range(pos, count, PCI_DEVICE_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		val16 = cpu_to_le16(0x1000);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (virtvdev->pci_cmd_io &&
> +	    range_contains_range(pos, count, PCI_COMMAND, sizeof(val16),
> +				 &copy_offset)) {
> +		if (copy_from_user(&val16, buf, sizeof(val16)))
> +			return -EFAULT;
> +		val16 |= cpu_to_le16(PCI_COMMAND_IO);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_REVISION_ID, sizeof(val8),
> +				 &copy_offset)) {
> +		/* Transional needs to have revision 0 */
> +		val8 = 0;
> +		if (copy_to_user(buf + copy_offset, &val8, sizeof(val8)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_BASE_ADDRESS_0, sizeof(val32),
> +				 &copy_offset)) {
> +		val32 = cpu_to_le32(PCI_BASE_ADDRESS_SPACE_IO);
> +		if (copy_to_user(buf + copy_offset, &val32, sizeof(val32)))
> +			return -EFAULT;
> +	}
> +
> +	if (range_contains_range(pos, count, PCI_SUBSYSTEM_ID, sizeof(val16),
> +				 &copy_offset)) {
> +		/* Transitional devices use the PCI subsystem device id as
> +		 * virtio device id, same as legacy driver always did.
> +		 */
> +		val16 = cpu_to_le16(VIRTIO_ID_NET);
> +		if (copy_to_user(buf + copy_offset, &val16, sizeof(val16)))
> +			return -EFAULT;
> +	}
> +
> +	return count;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_read(struct vfio_device *core_vdev, char __user *buf,
> +		       size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX)
> +		return virtiovf_pci_read_config(core_vdev, buf, count, ppos);
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_read(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n",
> +				     ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, buf, count, true);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static ssize_t
> +virtiovf_pci_core_write(struct vfio_device *core_vdev, const char __user
*buf,
> +			size_t count, loff_t *ppos)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev = virtvdev->core_device.pdev;
> +	unsigned int index = VFIO_PCI_OFFSET_TO_INDEX(*ppos);
> +	loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
> +	int ret;
> +
> +	if (!count)
> +		return 0;
> +
> +	if (index == VFIO_PCI_CONFIG_REGION_INDEX) {
> +		loff_t copy_offset;
> +		u16 cmd;
> +
> +		if (range_contains_range(pos, count, PCI_COMMAND, sizeof(cmd),
> +					 &copy_offset)) {
> +			if (copy_from_user(&cmd, buf + copy_offset, sizeof(cmd)))
> +				return -EFAULT;
> +			virtvdev->pci_cmd_io = (cmd & PCI_COMMAND_IO);
> +		}
> +	}
> +
> +	if (index != VFIO_PCI_BAR0_REGION_INDEX)
> +		return vfio_pci_core_write(core_vdev, buf, count, ppos);
> +
> +	ret = pm_runtime_resume_and_get(&pdev->dev);
> +	if (ret) {
> +		pci_info_ratelimited(pdev, "runtime resume failed %d\n", ret);
> +		return -EIO;
> +	}
> +
> +	ret = translate_io_bar_to_mem_bar(virtvdev, pos, (char __user *)buf,
count, false);
> +	pm_runtime_put(&pdev->dev);
> +	return ret;
> +}
> +
> +static int
> +virtiovf_pci_ioctl_get_region_info(struct vfio_device *core_vdev,
> +				   unsigned int cmd, unsigned long arg)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	unsigned long minsz = offsetofend(struct vfio_region_info, offset);
> +	void __user *uarg = (void __user *)arg;
> +	struct vfio_region_info info = {};
> +
> +	if (copy_from_user(&info, uarg, minsz))
> +		return -EFAULT;
> +
> +	if (info.argsz < minsz)
> +		return -EINVAL;
> +
> +	switch (info.index) {
> +	case VFIO_PCI_BAR0_REGION_INDEX:
> +		info.offset = VFIO_PCI_INDEX_TO_OFFSET(info.index);
> +		info.size = virtvdev->bar0_virtual_buf_size;
> +		info.flags = VFIO_REGION_INFO_FLAG_READ |
> +			     VFIO_REGION_INFO_FLAG_WRITE;
> +		return copy_to_user(uarg, &info, minsz) ? -EFAULT : 0;
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static long
> +virtiovf_vfio_pci_core_ioctl(struct vfio_device *core_vdev, unsigned int
cmd,
> +			     unsigned long arg)
> +{
> +	switch (cmd) {
> +	case VFIO_DEVICE_GET_REGION_INFO:
> +		return virtiovf_pci_ioctl_get_region_info(core_vdev, cmd, arg);
> +	default:
> +		return vfio_pci_core_ioctl(core_vdev, cmd, arg);
> +	}
> +}
> +
> +static int
> +virtiovf_set_notify_addr(struct virtiovf_pci_core_device *virtvdev)
> +{
> +	struct vfio_pci_core_device *core_device = &virtvdev->core_device;
> +	int ret;
> +
> +	/* Setup the BAR where the 'notify' exists to be used by vfio as
well
> +	 * This will let us mmap it only once and use it when needed.
> +	 */
> +	ret = vfio_pci_core_setup_barmap(core_device,
> +					 virtvdev->notify_bar);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_addr =
core_device->barmap[virtvdev->notify_bar] +
> +			virtvdev->notify_offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_open_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct vfio_pci_core_device *vdev = &virtvdev->core_device;
> +	int ret;
> +
> +	ret = vfio_pci_core_enable(vdev);
> +	if (ret)
> +		return ret;
> +
> +	if (virtvdev->bar0_virtual_buf) {
> +		/* upon close_device() the vfio_pci_core_disable() is called
> +		 * and will close all the previous mmaps, so it seems that the
> +		 * valid life cycle for the 'notify' addr is per open/close.
> +		 */
> +		ret = virtiovf_set_notify_addr(virtvdev);
> +		if (ret) {
> +			vfio_pci_core_disable(vdev);
> +			return ret;
> +		}
> +	}
> +
> +	vfio_pci_core_finish_enable(vdev);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_close_device(struct vfio_device *core_vdev)
> +{
> +	vfio_pci_core_close_device(core_vdev);
> +}
> +
> +static int virtiovf_get_device_config_size(unsigned short device)
> +{
> +	switch (device) {
> +	case 0x1041:
> +		/* network card */
> +		return offsetofend(struct virtio_net_config, status);
> +	default:
> +		return 0;
> +	}
> +}
> +
> +static int virtiovf_read_notify_info(struct virtiovf_pci_core_device
*virtvdev)
> +{
> +	u64 offset;
> +	int ret;
> +	u8 bar;
> +
> +	ret = virtiovf_cmd_lq_read_notify(virtvdev,
> +				VIRTIO_ADMIN_CMD_NOTIFY_INFO_FLAGS_OWNER_MEM,
> +				&bar, &offset);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->notify_bar = bar;
> +	virtvdev->notify_offset = offset;
> +	return 0;
> +}
> +
> +static int virtiovf_pci_init_device(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +	struct pci_dev *pdev;
> +	int ret;
> +
> +	ret = vfio_pci_core_init_dev(core_vdev);
> +	if (ret)
> +		return ret;
> +
> +	pdev = virtvdev->core_device.pdev;
> +	virtvdev->vf_id = pci_iov_vf_id(pdev);
> +	if (virtvdev->vf_id < 0)
> +		return -EINVAL;
> +
> +	ret = virtiovf_read_notify_info(virtvdev);
> +	if (ret)
> +		return ret;
> +
> +	virtvdev->bar0_virtual_buf_size = VIRTIO_LEGACY_IO_BAR_HEADER_LEN +
> +		VIRTIO_LEGACY_IO_BAR_MSIX_HEADER_LEN +
> +		virtiovf_get_device_config_size(pdev->device);
> +	virtvdev->bar0_virtual_buf =
kzalloc(virtvdev->bar0_virtual_buf_size,
> +					     GFP_KERNEL);
> +	if (!virtvdev->bar0_virtual_buf)
> +		return -ENOMEM;
> +	mutex_init(&virtvdev->bar_mutex);
> +	return 0;
> +}
> +
> +static void virtiovf_pci_core_release_dev(struct vfio_device *core_vdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev = container_of(
> +		core_vdev, struct virtiovf_pci_core_device, core_device.vdev);
> +
> +	kfree(virtvdev->bar0_virtual_buf);
> +	vfio_pci_core_release_dev(core_vdev);
> +}
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_tran_ops = {
> +	.name = "virtio-transitional-vfio-pci",
> +	.init = virtiovf_pci_init_device,
> +	.release = virtiovf_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = virtiovf_vfio_pci_core_ioctl,
> +	.read = virtiovf_pci_core_read,
> +	.write = virtiovf_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static const struct vfio_device_ops virtiovf_acc_vfio_pci_ops = {
> +	.name = "virtio-acc-vfio-pci",
> +	.init = vfio_pci_core_init_dev,
> +	.release = vfio_pci_core_release_dev,
> +	.open_device = virtiovf_pci_open_device,
> +	.close_device = virtiovf_pci_close_device,
> +	.ioctl = vfio_pci_core_ioctl,
> +	.device_feature = vfio_pci_core_ioctl_feature,
> +	.read = vfio_pci_core_read,
> +	.write = vfio_pci_core_write,
> +	.mmap = vfio_pci_core_mmap,
> +	.request = vfio_pci_core_request,
> +	.match = vfio_pci_core_match,
> +	.bind_iommufd = vfio_iommufd_physical_bind,
> +	.unbind_iommufd = vfio_iommufd_physical_unbind,
> +	.attach_ioas = vfio_iommufd_physical_attach_ioas,
> +};
> +
> +static bool virtiovf_bar0_exists(struct pci_dev *pdev)
> +{
> +	struct resource *res = pdev->resource;
> +
> +	return res->flags ? true : false;
> +}
> +
> +#define VIRTIOVF_USE_ADMIN_CMD_BITMAP \
> +	(BIT_ULL(VIRTIO_ADMIN_CMD_LIST_QUERY) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LIST_USE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_COMMON_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_WRITE) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_DEV_CFG_READ) | \
> +	 BIT_ULL(VIRTIO_ADMIN_CMD_LEGACY_NOTIFY_INFO))
> +
> +static bool virtiovf_support_legacy_access(struct pci_dev *pdev)
> +{
> +	int buf_size = DIV_ROUND_UP(VIRTIO_ADMIN_MAX_CMD_OPCODE, 64) * 8;
> +	u8 *buf;
> +	int ret;
> +
> +	/* Only virtio-net is supported/tested so far */
> +	if (pdev->device != 0x1041)
> +		return false;
> +
> +	buf = kzalloc(buf_size, GFP_KERNEL);
> +	if (!buf)
> +		return false;
> +
> +	ret = virtiovf_cmd_list_query(pdev, buf, buf_size);
> +	if (ret)
> +		goto end;
> +
> +	if ((le64_to_cpup((__le64 *)buf) & VIRTIOVF_USE_ADMIN_CMD_BITMAP)
!> +		VIRTIOVF_USE_ADMIN_CMD_BITMAP) {
> +		ret = -EOPNOTSUPP;
> +		goto end;
> +	}
> +
> +	/* confirm the used commands */
> +	memset(buf, 0, buf_size);
> +	*(__le64 *)buf = cpu_to_le64(VIRTIOVF_USE_ADMIN_CMD_BITMAP);
> +	ret = virtiovf_cmd_list_use(pdev, buf, buf_size);
> +
> +end:
> +	kfree(buf);
> +	return ret ? false : true;
> +}
> +
> +static int virtiovf_pci_probe(struct pci_dev *pdev,
> +			      const struct pci_device_id *id)
> +{
> +	const struct vfio_device_ops *ops = &virtiovf_acc_vfio_pci_ops;
> +	struct virtiovf_pci_core_device *virtvdev;
> +	int ret;
> +
> +	if (pdev->is_virtfn && virtiovf_support_legacy_access(pdev)
&&
> +	    !virtiovf_bar0_exists(pdev) && pdev->msix_cap)
I see this is the reason you set MSIX to true. But I think it's a
misunderstanding - that true means MSIX is enabled by guest, not that
it exists.

> +		ops = &virtiovf_acc_vfio_pci_tran_ops;


Actually, I remember there's a problem with just always doing
transitional and that is VIRTIO_F_ACCESS_PLATFORM - some configs just
break in weird ways as device will go through an iommu. It would be
nicer I think if userspace had the last word on whether it wants to
enable legacy or not, even if hardware supports that.

> +
> +	virtvdev = vfio_alloc_device(virtiovf_pci_core_device, core_device.vdev,
> +				     &pdev->dev, ops);
> +	if (IS_ERR(virtvdev))
> +		return PTR_ERR(virtvdev);
> +
> +	dev_set_drvdata(&pdev->dev, &virtvdev->core_device);
> +	ret = vfio_pci_core_register_device(&virtvdev->core_device);
> +	if (ret)
> +		goto out;
> +	return 0;
> +out:
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +	return ret;
> +}
> +
> +static void virtiovf_pci_remove(struct pci_dev *pdev)
> +{
> +	struct virtiovf_pci_core_device *virtvdev =
dev_get_drvdata(&pdev->dev);
> +
> +	vfio_pci_core_unregister_device(&virtvdev->core_device);
> +	vfio_put_device(&virtvdev->core_device.vdev);
> +}
> +
> +static const struct pci_device_id virtiovf_pci_table[] = {
> +	{ PCI_DRIVER_OVERRIDE_DEVICE_VFIO(PCI_VENDOR_ID_REDHAT_QUMRANET,
PCI_ANY_ID) },
> +	{}
> +};
> +
> +MODULE_DEVICE_TABLE(pci, virtiovf_pci_table);
> +
> +static struct pci_driver virtiovf_pci_driver = {
> +	.name = KBUILD_MODNAME,
> +	.id_table = virtiovf_pci_table,
> +	.probe = virtiovf_pci_probe,
> +	.remove = virtiovf_pci_remove,
> +	.err_handler = &vfio_pci_core_err_handlers,
> +	.driver_managed_dma = true,
> +};
> +
> +module_pci_driver(virtiovf_pci_driver);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("Yishai Hadas <yishaih at nvidia.com>");
> +MODULE_DESCRIPTION(
> +	"VIRTIO VFIO PCI - User Level meta-driver for VIRTIO device
family");
> -- 
> 2.27.0