Linux Virtualization - Nov 2018 - [PATCH v4 3/7] of: Allow the iommu-map property to omit untranslated devices

Implement the virtio-iommu driver, following specification v0.8 [1].

Changes since v3 [2]:
* Rebase onto v4.20-rc2. Patch 3 now touches drivers/of/base.c instead
  of drivers/pci/of.c, since the map_rid() function has moved.
* Removed the request timeout, that depended on DEBUG.
* Other small fixes addressing comments on v3.

You can find Linux driver and kvmtool device on my virtio-iommu/v0.8.1
branches [3]. You can also test it with the latest version of Eric's
QEMU device [4].

[1] Virtio-iommu specification v0.8, sources and pdf
    git://linux-arm.org/virtio-iommu.git virtio-iommu/v0.8
    http://jpbrucker.net/virtio-iommu/spec/v0.8/virtio-iommu-v0.8.pdf

[2] [PATCH v3 0/7] Add virtio-iommu driver
    https://www.spinics.net/lists/linux-pci/msg77110.html

[3] git://linux-arm.org/linux-jpb.git virtio-iommu/v0.8.1
    git://linux-arm.org/kvmtool-jpb.git virtio-iommu/v0.8.1

[4] [RFC v8 00/18] VIRTIO-IOMMU device
    https://www.mail-archive.com/qemu-devel at nongnu.org/msg572637.html

Jean-Philippe Brucker (7):
  dt-bindings: virtio-mmio: Add IOMMU description
  dt-bindings: virtio: Add virtio-pci-iommu node
  of: Allow the iommu-map property to omit untranslated devices
  PCI: OF: Initialize dev->fwnode appropriately
  iommu: Add virtio-iommu driver
  iommu/virtio: Add probe request
  iommu/virtio: Add event queue

 .../devicetree/bindings/virtio/iommu.txt      |   66 +
 .../devicetree/bindings/virtio/mmio.txt       |   30 +
 MAINTAINERS                                   |    7 +
 drivers/iommu/Kconfig                         |   11 +
 drivers/iommu/Makefile                        |    1 +
 drivers/iommu/virtio-iommu.c                  | 1160 +++++++++++++++++
 drivers/of/base.c                             |   10 +-
 drivers/pci/of.c                              |    7 +
 include/uapi/linux/virtio_ids.h               |    1 +
 include/uapi/linux/virtio_iommu.h             |  161 +++
 10 files changed, 1451 insertions(+), 3 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt
 create mode 100644 drivers/iommu/virtio-iommu.c
 create mode 100644 include/uapi/linux/virtio_iommu.h

-- 
2.19.1

The nature of a virtio-mmio node is discovered by the virtio driver at
probe time. However the DMA relation between devices must be described
statically. When a virtio-mmio node is a virtio-iommu device, it needs an
"#iommu-cells" property as specified by bindings/iommu/iommu.txt.

Otherwise, the virtio-mmio device may perform DMA through an IOMMU, which
requires an "iommus" property. Describe these requirements in the
device-tree bindings documentation.

Reviewed-by: Rob Herring <robh at kernel.org>
Reviewed-by: Eric Auger <eric.auger at redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 .../devicetree/bindings/virtio/mmio.txt       | 30 +++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/Documentation/devicetree/bindings/virtio/mmio.txt
b/Documentation/devicetree/bindings/virtio/mmio.txt
index 5069c1b8e193..21af30fbb81f 100644
--- a/Documentation/devicetree/bindings/virtio/mmio.txt
+++ b/Documentation/devicetree/bindings/virtio/mmio.txt
@@ -8,10 +8,40 @@ Required properties:
 - reg:		control registers base address and size including configuration space
 - interrupts:	interrupt generated by the device
 
+Required properties for virtio-iommu:
+
+- #iommu-cells:	When the node corresponds to a virtio-iommu device, it is
+		linked to DMA masters using the "iommus" or "iommu-map"
+		properties [1][2]. #iommu-cells specifies the size of the
+		"iommus" property. For virtio-iommu #iommu-cells must be
+		1, each cell describing a single endpoint ID.
+
+Optional properties:
+
+- iommus:	If the device accesses memory through an IOMMU, it should
+		have an "iommus" property [1]. Since virtio-iommu itself
+		does not access memory through an IOMMU, the "virtio,mmio"
+		node cannot have both an "#iommu-cells" and an "iommus"
+		property.
+
 Example:
 
 	virtio_block at 3000 {
 		compatible = "virtio,mmio";
 		reg = <0x3000 0x100>;
 		interrupts = <41>;
+
+		/* Device has endpoint ID 23 */
+		iommus = <&viommu 23>
 	}
+
+	viommu: iommu at 3100 {
+		compatible = "virtio,mmio";
+		reg = <0x3100 0x100>;
+		interrupts = <42>;
+
+		#iommu-cells = <1>
+	}
+
+[1] Documentation/devicetree/bindings/iommu/iommu.txt
+[2] Documentation/devicetree/bindings/pci/pci-iommu.txt
-- 
2.19.1

Some systems implement virtio-iommu as a PCI endpoint. The operating
system needs to discover the relationship between IOMMU and masters long
before the PCI endpoint gets probed. Add a PCI child node to describe the
virtio-iommu device.

The virtio-pci-iommu is conceptually split between a PCI programming
interface and a translation component on the parent bus. The latter
doesn't have a node in the device tree. The virtio-pci-iommu node
describes both, by linking the PCI endpoint to "iommus" property of
DMA
master nodes and to "iommu-map" properties of bus nodes.

Reviewed-by: Rob Herring <robh at kernel.org>
Reviewed-by: Eric Auger <eric.auger at redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 .../devicetree/bindings/virtio/iommu.txt      | 66 +++++++++++++++++++
 1 file changed, 66 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt

diff --git a/Documentation/devicetree/bindings/virtio/iommu.txt
b/Documentation/devicetree/bindings/virtio/iommu.txt
new file mode 100644
index 000000000000..2407fea0651c
--- /dev/null
+++ b/Documentation/devicetree/bindings/virtio/iommu.txt
@@ -0,0 +1,66 @@
+* virtio IOMMU PCI device
+
+When virtio-iommu uses the PCI transport, its programming interface is
+discovered dynamically by the PCI probing infrastructure. However the
+device tree statically describes the relation between IOMMU and DMA
+masters. Therefore, the PCI root complex that hosts the virtio-iommu
+contains a child node representing the IOMMU device explicitly.
+
+Required properties:
+
+- compatible:	Should be "virtio,pci-iommu"
+- reg:		PCI address of the IOMMU. As defined in the PCI Bus
+		Binding reference [1], the reg property is a five-cell
+		address encoded as (phys.hi phys.mid phys.lo size.hi
+		size.lo). phys.hi should contain the device's BDF as
+		0b00000000 bbbbbbbb dddddfff 00000000. The other cells
+		should be zero.
+- #iommu-cells:	Each platform DMA master managed by the IOMMU is assigned
+		an endpoint ID, described by the "iommus" property [2].
+		For virtio-iommu, #iommu-cells must be 1.
+
+Notes:
+
+- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
+  virtio-iommu node doesn't have an "iommus" property, and is
omitted from
+  the iommu-map property of the root complex.
+
+Example:
+
+pcie at 10000000 {
+	compatible = "pci-host-ecam-generic";
+	...
+
+	/* The IOMMU programming interface uses slot 00:01.0 */
+	iommu0: iommu at 0008 {
+		compatible = "virtio,pci-iommu";
+		reg = <0x00000800 0 0 0 0>;
+		#iommu-cells = <1>;
+	};
+
+	/*
+	 * The IOMMU manages all functions in this PCI domain except
+	 * itself. Omit BDF 00:01.0.
+	 */
+	iommu-map = <0x0 &iommu0 0x0 0x8>
+		    <0x9 &iommu0 0x9 0xfff7>;
+};
+
+pcie at 20000000 {
+	compatible = "pci-host-ecam-generic";
+	...
+	/*
+	 * The IOMMU also manages all functions from this domain,
+	 * with endpoint IDs 0x10000 - 0x1ffff
+	 */
+	iommu-map = <0x0 &iommu0 0x10000 0x10000>;
+};
+
+ethernet at fe001000 {
+	...
+	/* The IOMMU manages this platform device with endpoint ID 0x20000 */
+	iommus = <&iommu0 0x20000>;
+};
+
+[1] Documentation/devicetree/bindings/pci/pci.txt
+[2] Documentation/devicetree/bindings/iommu/iommu.txt
-- 
2.19.1

In PCI root complex nodes, the iommu-map property describes the IOMMU that
translates each endpoint. On some platforms, the IOMMU itself is presented
as a PCI endpoint (e.g. AMD IOMMU and virtio-iommu). This isn't supported
by the current OF driver, which expects all endpoints to have an IOMMU.
Allow the iommu-map property to have gaps.

Relaxing of_map_rid() also allows the msi-map property to have gaps, which
is invalid since MSIs always reach an MSI controller. In that case
pci_msi_setup_msi_irqs() will return an error when attempting to find the
device's MSI domain.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 drivers/of/base.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index 09692c9b32a7..99f6bfa9b898 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -2237,8 +2237,12 @@ int of_map_rid(struct device_node *np, u32 rid,
 		return 0;
 	}
 
-	pr_err("%pOF: Invalid %s translation - no match for rid 0x%x on
%pOF\n",
-		np, map_name, rid, target && *target ? *target : NULL);
-	return -EFAULT;
+	pr_info("%pOF: no %s translation for rid 0x%x on %pOF\n", np,
map_name,
+		rid, target && *target ? *target : NULL);
+
+	/* Bypasses translation */
+	if (id_out)
+		*id_out = rid;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(of_map_rid);
-- 
2.19.1

For PCI devices that have an OF node, set the fwnode as well. This way
drivers that rely on fwnode don't need the special case described by
commit f94277af03ea ("of/platform: Initialise dev->fwnode
appropriately").

Acked-by: Bjorn Helgaas <bhelgaas at google.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 drivers/pci/of.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 4c4217d0c3f1..c272ecfcd038 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -21,12 +21,15 @@ void pci_set_of_node(struct pci_dev *dev)
 		return;
 	dev->dev.of_node = of_pci_find_child_device(dev->bus->dev.of_node,
 						    dev->devfn);
+	if (dev->dev.of_node)
+		dev->dev.fwnode = &dev->dev.of_node->fwnode;
 }
 
 void pci_release_of_node(struct pci_dev *dev)
 {
 	of_node_put(dev->dev.of_node);
 	dev->dev.of_node = NULL;
+	dev->dev.fwnode = NULL;
 }
 
 void pci_set_bus_of_node(struct pci_bus *bus)
@@ -35,12 +38,16 @@ void pci_set_bus_of_node(struct pci_bus *bus)
 		bus->dev.of_node = pcibios_get_phb_of_node(bus);
 	else
 		bus->dev.of_node = of_node_get(bus->self->dev.of_node);
+
+	if (bus->dev.of_node)
+		bus->dev.fwnode = &bus->dev.of_node->fwnode;
 }
 
 void pci_release_bus_of_node(struct pci_bus *bus)
 {
 	of_node_put(bus->dev.of_node);
 	bus->dev.of_node = NULL;
+	bus->dev.fwnode = NULL;
 }
 
 struct device_node * __weak pcibios_get_phb_of_node(struct pci_bus *bus)
-- 
2.19.1

The virtio IOMMU is a para-virtualized device, allowing to send IOMMU
requests such as map/unmap over virtio transport without emulating page
tables. This implementation handles ATTACH, DETACH, MAP and UNMAP
requests.

The bulk of the code transforms calls coming from the IOMMU API into
corresponding virtio requests. Mappings are kept in an interval tree
instead of page tables.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 MAINTAINERS                       |   7 +
 drivers/iommu/Kconfig             |  11 +
 drivers/iommu/Makefile            |   1 +
 drivers/iommu/virtio-iommu.c      | 918 ++++++++++++++++++++++++++++++
 include/uapi/linux/virtio_ids.h   |   1 +
 include/uapi/linux/virtio_iommu.h | 104 ++++
 6 files changed, 1042 insertions(+)
 create mode 100644 drivers/iommu/virtio-iommu.c
 create mode 100644 include/uapi/linux/virtio_iommu.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 0abecc528dac..0c7bdce57719 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -15948,6 +15948,13 @@ S:	Maintained
 F:	drivers/virtio/virtio_input.c
 F:	include/uapi/linux/virtio_input.h
 
+VIRTIO IOMMU DRIVER
+M:	Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
+L:	virtualization at lists.linux-foundation.org
+S:	Maintained
+F:	drivers/iommu/virtio-iommu.c
+F:	include/uapi/linux/virtio_iommu.h
+
 VIRTUAL BOX GUEST DEVICE DRIVER
 M:	Hans de Goede <hdegoede at redhat.com>
 M:	Arnd Bergmann <arnd at arndb.de>
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index d9a25715650e..efdeaaeee0e0 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -435,4 +435,15 @@ config QCOM_IOMMU
 	help
 	  Support for IOMMU on certain Qualcomm SoCs.
 
+config VIRTIO_IOMMU
+	bool "Virtio IOMMU driver"
+	depends on VIRTIO=y
+	select IOMMU_API
+	select INTERVAL_TREE
+	select ARM_DMA_USE_IOMMU if ARM
+	help
+	  Para-virtualised IOMMU driver with virtio.
+
+	  Say Y here if you intend to run this kernel as a guest.
+
 endif # IOMMU_SUPPORT
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index a158a68c8ea8..48d831a39281 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -32,3 +32,4 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
 obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
 obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
 obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
+obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
new file mode 100644
index 000000000000..2a9cb6285a1e
--- /dev/null
+++ b/drivers/iommu/virtio-iommu.c
@@ -0,0 +1,918 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Virtio driver for the paravirtualized IOMMU
+ *
+ * Copyright (C) 2018 Arm Limited
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/amba/bus.h>
+#include <linux/delay.h>
+#include <linux/dma-iommu.h>
+#include <linux/freezer.h>
+#include <linux/interval_tree.h>
+#include <linux/iommu.h>
+#include <linux/module.h>
+#include <linux/of_iommu.h>
+#include <linux/of_platform.h>
+#include <linux/pci.h>
+#include <linux/platform_device.h>
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/virtio_ids.h>
+#include <linux/wait.h>
+
+#include <uapi/linux/virtio_iommu.h>
+
+#define MSI_IOVA_BASE			0x8000000
+#define MSI_IOVA_LENGTH			0x100000
+
+#define VIOMMU_REQUEST_VQ		0
+#define VIOMMU_NR_VQS			1
+
+struct viommu_dev {
+	struct iommu_device		iommu;
+	struct device			*dev;
+	struct virtio_device		*vdev;
+
+	struct ida			domain_ids;
+
+	struct virtqueue		*vqs[VIOMMU_NR_VQS];
+	spinlock_t			request_lock;
+	struct list_head		requests;
+
+	/* Device configuration */
+	struct iommu_domain_geometry	geometry;
+	u64				pgsize_bitmap;
+	u8				domain_bits;
+};
+
+struct viommu_mapping {
+	phys_addr_t			paddr;
+	struct interval_tree_node	iova;
+	u32				flags;
+};
+
+struct viommu_domain {
+	struct iommu_domain		domain;
+	struct viommu_dev		*viommu;
+	struct mutex			mutex;
+	unsigned int			id;
+
+	spinlock_t			mappings_lock;
+	struct rb_root_cached		mappings;
+
+	unsigned long			nr_endpoints;
+};
+
+struct viommu_endpoint {
+	struct viommu_dev		*viommu;
+	struct viommu_domain		*vdomain;
+};
+
+struct viommu_request {
+	struct list_head		list;
+	void				*writeback;
+	unsigned int			write_offset;
+	unsigned int			len;
+	char				buf[];
+};
+
+#define to_viommu_domain(domain)	\
+	container_of(domain, struct viommu_domain, domain)
+
+static int viommu_get_req_errno(void *buf, size_t len)
+{
+	struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);
+
+	switch (tail->status) {
+	case VIRTIO_IOMMU_S_OK:
+		return 0;
+	case VIRTIO_IOMMU_S_UNSUPP:
+		return -ENOSYS;
+	case VIRTIO_IOMMU_S_INVAL:
+		return -EINVAL;
+	case VIRTIO_IOMMU_S_RANGE:
+		return -ERANGE;
+	case VIRTIO_IOMMU_S_NOENT:
+		return -ENOENT;
+	case VIRTIO_IOMMU_S_FAULT:
+		return -EFAULT;
+	case VIRTIO_IOMMU_S_IOERR:
+	case VIRTIO_IOMMU_S_DEVERR:
+	default:
+		return -EIO;
+	}
+}
+
+static void viommu_set_req_status(void *buf, size_t len, int status)
+{
+	struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);
+
+	tail->status = status;
+}
+
+static off_t viommu_get_req_offset(struct viommu_dev *viommu,
+				   struct virtio_iommu_req_head *req,
+				   size_t len)
+{
+	size_t tail_size = sizeof(struct virtio_iommu_req_tail);
+
+	return len - tail_size;
+}
+
+/*
+ * __viommu_sync_req - Complete all in-flight requests
+ *
+ * Wait for all added requests to complete. When this function returns, all
+ * requests that were in-flight at the time of the call have completed.
+ */
+static int __viommu_sync_req(struct viommu_dev *viommu)
+{
+	int ret = 0;
+	unsigned int len;
+	size_t write_len;
+	struct viommu_request *req;
+	struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];
+
+	assert_spin_locked(&viommu->request_lock);
+
+	virtqueue_kick(vq);
+
+	while (!list_empty(&viommu->requests)) {
+		len = 0;
+		req = virtqueue_get_buf(vq, &len);
+		if (!req)
+			continue;
+
+		if (!len)
+			viommu_set_req_status(req->buf, req->len,
+					      VIRTIO_IOMMU_S_IOERR);
+
+		write_len = req->len - req->write_offset;
+		if (req->writeback && len >= write_len)
+			memcpy(req->writeback, req->buf + req->write_offset,
+			       write_len);
+
+		list_del(&req->list);
+		kfree(req);
+	}
+
+	return ret;
+}
+
+static int viommu_sync_req(struct viommu_dev *viommu)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&viommu->request_lock, flags);
+	ret = __viommu_sync_req(viommu);
+	if (ret)
+		dev_dbg(viommu->dev, "could not sync requests (%d)\n", ret);
+	spin_unlock_irqrestore(&viommu->request_lock, flags);
+
+	return ret;
+}
+
+/*
+ * __viommu_add_request - Add one request to the queue
+ * @buf: pointer to the request buffer
+ * @len: length of the request buffer
+ * @writeback: copy data back to the buffer when the request completes.
+ *
+ * Add a request to the queue. Only synchronize the queue if it's already
full.
+ * Otherwise don't kick the queue nor wait for requests to complete.
+ *
+ * When @writeback is true, data written by the device, including the request
+ * status, is copied into @buf after the request completes. This is unsafe if
+ * the caller allocates @buf on stack and drops the lock between add_req() and
+ * sync_req().
+ *
+ * Return 0 if the request was successfully added to the queue.
+ */
+static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len,
+			    bool writeback)
+{
+	int ret;
+	off_t write_offset;
+	struct viommu_request *req;
+	struct scatterlist top_sg, bottom_sg;
+	struct scatterlist *sg[2] = { &top_sg, &bottom_sg };
+	struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];
+
+	assert_spin_locked(&viommu->request_lock);
+
+	write_offset = viommu_get_req_offset(viommu, buf, len);
+	if (!write_offset)
+		return -EINVAL;
+
+	req = kzalloc(sizeof(*req) + len, GFP_ATOMIC);
+	if (!req)
+		return -ENOMEM;
+
+	req->len = len;
+	if (writeback) {
+		req->writeback = buf + write_offset;
+		req->write_offset = write_offset;
+	}
+	memcpy(&req->buf, buf, write_offset);
+
+	sg_init_one(&top_sg, req->buf, write_offset);
+	sg_init_one(&bottom_sg, req->buf + write_offset, len - write_offset);
+
+	ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
+	if (ret == -ENOSPC) {
+		/* If the queue is full, sync and retry */
+		if (!__viommu_sync_req(viommu))
+			ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
+	}
+	if (ret)
+		goto err_free;
+
+	list_add_tail(&req->list, &viommu->requests);
+	return 0;
+
+err_free:
+	kfree(req);
+	return ret;
+}
+
+static int viommu_add_req(struct viommu_dev *viommu, void *buf, size_t len)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&viommu->request_lock, flags);
+	ret = __viommu_add_req(viommu, buf, len, false);
+	if (ret)
+		dev_dbg(viommu->dev, "could not add request: %d\n", ret);
+	spin_unlock_irqrestore(&viommu->request_lock, flags);
+
+	return ret;
+}
+
+/*
+ * Send a request and wait for it to complete. Return the request status (as an
+ * errno)
+ */
+static int viommu_send_req_sync(struct viommu_dev *viommu, void *buf,
+				size_t len)
+{
+	int ret;
+	unsigned long flags;
+
+	spin_lock_irqsave(&viommu->request_lock, flags);
+
+	ret = __viommu_add_req(viommu, buf, len, true);
+	if (ret) {
+		dev_dbg(viommu->dev, "could not add request (%d)\n", ret);
+		goto out_unlock;
+	}
+
+	ret = __viommu_sync_req(viommu);
+	if (ret) {
+		dev_dbg(viommu->dev, "could not sync requests (%d)\n", ret);
+		/* Fall-through (get the actual request status) */
+	}
+
+	ret = viommu_get_req_errno(buf, len);
+out_unlock:
+	spin_unlock_irqrestore(&viommu->request_lock, flags);
+	return ret;
+}
+
+/*
+ * viommu_add_mapping - add a mapping to the internal tree
+ *
+ * On success, return the new mapping. Otherwise return NULL.
+ */
+static struct viommu_mapping *
+viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
+		   phys_addr_t paddr, size_t size, u32 flags)
+{
+	unsigned long irqflags;
+	struct viommu_mapping *mapping;
+
+	mapping = kzalloc(sizeof(*mapping), GFP_ATOMIC);
+	if (!mapping)
+		return NULL;
+
+	mapping->paddr		= paddr;
+	mapping->iova.start	= iova;
+	mapping->iova.last	= iova + size - 1;
+	mapping->flags		= flags;
+
+	spin_lock_irqsave(&vdomain->mappings_lock, irqflags);
+	interval_tree_insert(&mapping->iova, &vdomain->mappings);
+	spin_unlock_irqrestore(&vdomain->mappings_lock, irqflags);
+
+	return mapping;
+}
+
+/*
+ * viommu_del_mappings - remove mappings from the internal tree
+ *
+ * @vdomain: the domain
+ * @iova: start of the range
+ * @size: size of the range. A size of 0 corresponds to the entire address
+ *	space.
+ *
+ * On success, returns the number of unmapped bytes (>= size)
+ */
+static size_t viommu_del_mappings(struct viommu_domain *vdomain,
+				  unsigned long iova, size_t size)
+{
+	size_t unmapped = 0;
+	unsigned long flags;
+	unsigned long last = iova + size - 1;
+	struct viommu_mapping *mapping = NULL;
+	struct interval_tree_node *node, *next;
+
+	spin_lock_irqsave(&vdomain->mappings_lock, flags);
+	next = interval_tree_iter_first(&vdomain->mappings, iova, last);
+	while (next) {
+		node = next;
+		mapping = container_of(node, struct viommu_mapping, iova);
+		next = interval_tree_iter_next(node, iova, last);
+
+		/* Trying to split a mapping? */
+		if (mapping->iova.start < iova)
+			break;
+
+		/*
+		 * Note that for a partial range, this will return the full
+		 * mapping so we avoid sending split requests to the device.
+		 */
+		unmapped += mapping->iova.last - mapping->iova.start + 1;
+
+		interval_tree_remove(node, &vdomain->mappings);
+		kfree(mapping);
+	}
+	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
+
+	return unmapped;
+}
+
+/*
+ * viommu_replay_mappings - re-send MAP requests
+ *
+ * When reattaching a domain that was previously detached from all endpoints,
+ * mappings were deleted from the device. Re-create the mappings available in
+ * the internal tree.
+ */
+static int viommu_replay_mappings(struct viommu_domain *vdomain)
+{
+	int ret = 0;
+	unsigned long flags;
+	struct viommu_mapping *mapping;
+	struct interval_tree_node *node;
+	struct virtio_iommu_req_map map;
+
+	spin_lock_irqsave(&vdomain->mappings_lock, flags);
+	node = interval_tree_iter_first(&vdomain->mappings, 0, -1UL);
+	while (node) {
+		mapping = container_of(node, struct viommu_mapping, iova);
+		map = (struct virtio_iommu_req_map) {
+			.head.type	= VIRTIO_IOMMU_T_MAP,
+			.domain		= cpu_to_le32(vdomain->id),
+			.virt_start	= cpu_to_le64(mapping->iova.start),
+			.virt_end	= cpu_to_le64(mapping->iova.last),
+			.phys_start	= cpu_to_le64(mapping->paddr),
+			.flags		= cpu_to_le32(mapping->flags),
+		};
+
+		ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
+		if (ret)
+			break;
+
+		node = interval_tree_iter_next(node, 0, -1UL);
+	}
+	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
+
+	return ret;
+}
+
+/* IOMMU API */
+
+static struct iommu_domain *viommu_domain_alloc(unsigned type)
+{
+	struct viommu_domain *vdomain;
+
+	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
+		return NULL;
+
+	vdomain = kzalloc(sizeof(*vdomain), GFP_KERNEL);
+	if (!vdomain)
+		return NULL;
+
+	mutex_init(&vdomain->mutex);
+	spin_lock_init(&vdomain->mappings_lock);
+	vdomain->mappings = RB_ROOT_CACHED;
+
+	if (type == IOMMU_DOMAIN_DMA &&
+	    iommu_get_dma_cookie(&vdomain->domain)) {
+		kfree(vdomain);
+		return NULL;
+	}
+
+	return &vdomain->domain;
+}
+
+static int viommu_domain_finalise(struct viommu_dev *viommu,
+				  struct iommu_domain *domain)
+{
+	int ret;
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+	unsigned int max_domain = viommu->domain_bits > 31 ? ~0 :
+				  (1U << viommu->domain_bits) - 1;
+
+	vdomain->viommu		= viommu;
+
+	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
+	domain->geometry	= viommu->geometry;
+
+	ret = ida_alloc_max(&viommu->domain_ids, max_domain, GFP_KERNEL);
+	if (ret >= 0)
+		vdomain->id = (unsigned int)ret;
+
+	return ret > 0 ? 0 : ret;
+}
+
+static void viommu_domain_free(struct iommu_domain *domain)
+{
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	iommu_put_dma_cookie(domain);
+
+	/* Free all remaining mappings (size 2^64) */
+	viommu_del_mappings(vdomain, 0, 0);
+
+	if (vdomain->viommu)
+		ida_free(&vdomain->viommu->domain_ids, vdomain->id);
+
+	kfree(vdomain);
+}
+
+static int viommu_attach_dev(struct iommu_domain *domain, struct device *dev)
+{
+	int i;
+	int ret = 0;
+	struct virtio_iommu_req_attach req;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+	struct viommu_endpoint *vdev = fwspec->iommu_priv;
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	mutex_lock(&vdomain->mutex);
+	if (!vdomain->viommu) {
+		/*
+		 * Initialize the domain proper now that we know which viommu
+		 * owns it.
+		 */
+		ret = viommu_domain_finalise(vdev->viommu, domain);
+	} else if (vdomain->viommu != vdev->viommu) {
+		dev_err(dev, "cannot attach to foreign vIOMMU\n");
+		ret = -EXDEV;
+	}
+	mutex_unlock(&vdomain->mutex);
+
+	if (ret)
+		return ret;
+
+	/*
+	 * In the virtio-iommu device, when attaching the endpoint to a new
+	 * domain, it is detached from the old one and, if as as a result the
+	 * old domain isn't attached to any endpoint, all mappings are removed
+	 * from the old domain and it is freed.
+	 *
+	 * In the driver the old domain still exists, and its mappings will be
+	 * recreated if it gets reattached to an endpoint. Otherwise it will be
+	 * freed explicitly.
+	 *
+	 * vdev->vdomain is protected by group->mutex
+	 */
+	if (vdev->vdomain)
+		vdev->vdomain->nr_endpoints--;
+
+	req = (struct virtio_iommu_req_attach) {
+		.head.type	= VIRTIO_IOMMU_T_ATTACH,
+		.domain		= cpu_to_le32(vdomain->id),
+	};
+
+	for (i = 0; i < fwspec->num_ids; i++) {
+		req.endpoint = cpu_to_le32(fwspec->ids[i]);
+
+		ret = viommu_send_req_sync(vdomain->viommu, &req, sizeof(req));
+		if (ret)
+			return ret;
+	}
+
+	if (!vdomain->nr_endpoints) {
+		/*
+		 * This endpoint is the first to be attached to the domain.
+		 * Replay existing mappings (e.g. SW MSI).
+		 */
+		ret = viommu_replay_mappings(vdomain);
+		if (ret)
+			return ret;
+	}
+
+	vdomain->nr_endpoints++;
+	vdev->vdomain = vdomain;
+
+	return 0;
+}
+
+static int viommu_map(struct iommu_domain *domain, unsigned long iova,
+		      phys_addr_t paddr, size_t size, int prot)
+{
+	int ret;
+	int flags;
+	struct viommu_mapping *mapping;
+	struct virtio_iommu_req_map map;
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	flags = (prot & IOMMU_READ ? VIRTIO_IOMMU_MAP_F_READ : 0) |
+		(prot & IOMMU_WRITE ? VIRTIO_IOMMU_MAP_F_WRITE : 0) |
+		(prot & IOMMU_MMIO ? VIRTIO_IOMMU_MAP_F_MMIO : 0);
+
+	mapping = viommu_add_mapping(vdomain, iova, paddr, size, flags);
+	if (!mapping)
+		return -ENOMEM;
+
+	map = (struct virtio_iommu_req_map) {
+		.head.type	= VIRTIO_IOMMU_T_MAP,
+		.domain		= cpu_to_le32(vdomain->id),
+		.virt_start	= cpu_to_le64(iova),
+		.phys_start	= cpu_to_le64(paddr),
+		.virt_end	= cpu_to_le64(iova + size - 1),
+		.flags		= cpu_to_le32(flags),
+	};
+
+	if (!vdomain->nr_endpoints)
+		return 0;
+
+	ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
+	if (ret)
+		viommu_del_mappings(vdomain, iova, size);
+
+	return ret;
+}
+
+static size_t viommu_unmap(struct iommu_domain *domain, unsigned long iova,
+			   size_t size)
+{
+	int ret = 0;
+	size_t unmapped;
+	struct virtio_iommu_req_unmap unmap;
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	unmapped = viommu_del_mappings(vdomain, iova, size);
+	if (unmapped < size)
+		return 0;
+
+	/* Device already removed all mappings after detach. */
+	if (!vdomain->nr_endpoints)
+		return unmapped;
+
+	unmap = (struct virtio_iommu_req_unmap) {
+		.head.type	= VIRTIO_IOMMU_T_UNMAP,
+		.domain		= cpu_to_le32(vdomain->id),
+		.virt_start	= cpu_to_le64(iova),
+		.virt_end	= cpu_to_le64(iova + unmapped - 1),
+	};
+
+	ret = viommu_add_req(vdomain->viommu, &unmap, sizeof(unmap));
+	return ret ? 0 : unmapped;
+}
+
+static phys_addr_t viommu_iova_to_phys(struct iommu_domain *domain,
+				       dma_addr_t iova)
+{
+	u64 paddr = 0;
+	unsigned long flags;
+	struct viommu_mapping *mapping;
+	struct interval_tree_node *node;
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	spin_lock_irqsave(&vdomain->mappings_lock, flags);
+	node = interval_tree_iter_first(&vdomain->mappings, iova, iova);
+	if (node) {
+		mapping = container_of(node, struct viommu_mapping, iova);
+		paddr = mapping->paddr + (iova - mapping->iova.start);
+	}
+	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
+
+	return paddr;
+}
+
+static void viommu_iotlb_sync(struct iommu_domain *domain)
+{
+	struct viommu_domain *vdomain = to_viommu_domain(domain);
+
+	viommu_sync_req(vdomain->viommu);
+}
+
+static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
+{
+	struct iommu_resv_region *region;
+	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
+
+	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
+					 IOMMU_RESV_SW_MSI);
+	if (!region)
+		return;
+
+	list_add_tail(&region->list, head);
+	iommu_dma_get_resv_regions(dev, head);
+}
+
+static void viommu_put_resv_regions(struct device *dev, struct list_head *head)
+{
+	struct iommu_resv_region *entry, *next;
+
+	list_for_each_entry_safe(entry, next, head, list)
+		kfree(entry);
+}
+
+static struct iommu_ops viommu_ops;
+static struct virtio_driver virtio_iommu_drv;
+
+static int viommu_match_node(struct device *dev, void *data)
+{
+	return dev->parent->fwnode == data;
+}
+
+static struct viommu_dev *viommu_get_by_fwnode(struct fwnode_handle *fwnode)
+{
+	struct device *dev = driver_find_device(&virtio_iommu_drv.driver, NULL,
+						fwnode, viommu_match_node);
+	put_device(dev);
+
+	return dev ? dev_to_virtio(dev)->priv : NULL;
+}
+
+static int viommu_add_device(struct device *dev)
+{
+	int ret;
+	struct iommu_group *group;
+	struct viommu_endpoint *vdev;
+	struct viommu_dev *viommu = NULL;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+
+	if (!fwspec || fwspec->ops != &viommu_ops)
+		return -ENODEV;
+
+	viommu = viommu_get_by_fwnode(fwspec->iommu_fwnode);
+	if (!viommu)
+		return -ENODEV;
+
+	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
+	if (!vdev)
+		return -ENOMEM;
+
+	vdev->viommu = viommu;
+	fwspec->iommu_priv = vdev;
+
+	ret = iommu_device_link(&viommu->iommu, dev);
+	if (ret)
+		goto err_free_dev;
+
+	/*
+	 * Last step creates a default domain and attaches to it. Everything
+	 * must be ready.
+	 */
+	group = iommu_group_get_for_dev(dev);
+	if (IS_ERR(group)) {
+		ret = PTR_ERR(group);
+		goto err_unlink_dev;
+	}
+
+	iommu_group_put(group);
+
+	return PTR_ERR_OR_ZERO(group);
+
+err_unlink_dev:
+	iommu_device_unlink(&viommu->iommu, dev);
+err_free_dev:
+	kfree(vdev);
+
+	return ret;
+}
+
+static void viommu_remove_device(struct device *dev)
+{
+	struct viommu_endpoint *vdev;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+
+	if (!fwspec || fwspec->ops != &viommu_ops)
+		return;
+
+	vdev = fwspec->iommu_priv;
+
+	iommu_group_remove_device(dev);
+	iommu_device_unlink(&vdev->viommu->iommu, dev);
+	kfree(vdev);
+}
+
+static struct iommu_group *viommu_device_group(struct device *dev)
+{
+	if (dev_is_pci(dev))
+		return pci_device_group(dev);
+	else
+		return generic_device_group(dev);
+}
+
+static int viommu_of_xlate(struct device *dev, struct of_phandle_args *args)
+{
+	return iommu_fwspec_add_ids(dev, args->args, 1);
+}
+
+static struct iommu_ops viommu_ops = {
+	.domain_alloc		= viommu_domain_alloc,
+	.domain_free		= viommu_domain_free,
+	.attach_dev		= viommu_attach_dev,
+	.map			= viommu_map,
+	.unmap			= viommu_unmap,
+	.iova_to_phys		= viommu_iova_to_phys,
+	.iotlb_sync		= viommu_iotlb_sync,
+	.add_device		= viommu_add_device,
+	.remove_device		= viommu_remove_device,
+	.device_group		= viommu_device_group,
+	.get_resv_regions	= viommu_get_resv_regions,
+	.put_resv_regions	= viommu_put_resv_regions,
+	.of_xlate		= viommu_of_xlate,
+};
+
+static int viommu_init_vqs(struct viommu_dev *viommu)
+{
+	struct virtio_device *vdev = dev_to_virtio(viommu->dev);
+	const char *name = "request";
+	void *ret;
+
+	ret = virtio_find_single_vq(vdev, NULL, name);
+	if (IS_ERR(ret)) {
+		dev_err(viommu->dev, "cannot find VQ\n");
+		return PTR_ERR(ret);
+	}
+
+	viommu->vqs[VIOMMU_REQUEST_VQ] = ret;
+
+	return 0;
+}
+
+static int viommu_probe(struct virtio_device *vdev)
+{
+	struct device *parent_dev = vdev->dev.parent;
+	struct viommu_dev *viommu = NULL;
+	struct device *dev = &vdev->dev;
+	u64 input_start = 0;
+	u64 input_end = -1UL;
+	int ret;
+
+	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
+	    !virtio_has_feature(vdev, VIRTIO_IOMMU_F_MAP_UNMAP))
+		return -ENODEV;
+
+	viommu = devm_kzalloc(dev, sizeof(*viommu), GFP_KERNEL);
+	if (!viommu)
+		return -ENOMEM;
+
+	spin_lock_init(&viommu->request_lock);
+	ida_init(&viommu->domain_ids);
+	viommu->dev = dev;
+	viommu->vdev = vdev;
+	INIT_LIST_HEAD(&viommu->requests);
+
+	ret = viommu_init_vqs(viommu);
+	if (ret)
+		return ret;
+
+	virtio_cread(vdev, struct virtio_iommu_config, page_size_mask,
+		     &viommu->pgsize_bitmap);
+
+	if (!viommu->pgsize_bitmap) {
+		ret = -EINVAL;
+		goto err_free_vqs;
+	}
+
+	viommu->domain_bits = 32;
+
+	/* Optional features */
+	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
+			     struct virtio_iommu_config, input_range.start,
+			     &input_start);
+
+	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
+			     struct virtio_iommu_config, input_range.end,
+			     &input_end);
+
+	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_DOMAIN_BITS,
+			     struct virtio_iommu_config, domain_bits,
+			     &viommu->domain_bits);
+
+	viommu->geometry = (struct iommu_domain_geometry) {
+		.aperture_start	= input_start,
+		.aperture_end	= input_end,
+		.force_aperture	= true,
+	};
+
+	viommu_ops.pgsize_bitmap = viommu->pgsize_bitmap;
+
+	virtio_device_ready(vdev);
+
+	ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL, "%s",
+				     virtio_bus_name(vdev));
+	if (ret)
+		goto err_free_vqs;
+
+	iommu_device_set_ops(&viommu->iommu, &viommu_ops);
+	iommu_device_set_fwnode(&viommu->iommu, parent_dev->fwnode);
+
+	iommu_device_register(&viommu->iommu);
+
+#ifdef CONFIG_PCI
+	if (pci_bus_type.iommu_ops != &viommu_ops) {
+		pci_request_acs();
+		ret = bus_set_iommu(&pci_bus_type, &viommu_ops);
+		if (ret)
+			goto err_unregister;
+	}
+#endif
+#ifdef CONFIG_ARM_AMBA
+	if (amba_bustype.iommu_ops != &viommu_ops) {
+		ret = bus_set_iommu(&amba_bustype, &viommu_ops);
+		if (ret)
+			goto err_unregister;
+	}
+#endif
+	if (platform_bus_type.iommu_ops != &viommu_ops) {
+		ret = bus_set_iommu(&platform_bus_type, &viommu_ops);
+		if (ret)
+			goto err_unregister;
+	}
+
+	vdev->priv = viommu;
+
+	dev_info(dev, "input address: %u bits\n",
+		 order_base_2(viommu->geometry.aperture_end));
+	dev_info(dev, "page mask: %#llx\n", viommu->pgsize_bitmap);
+
+	return 0;
+
+err_unregister:
+	iommu_device_sysfs_remove(&viommu->iommu);
+	iommu_device_unregister(&viommu->iommu);
+err_free_vqs:
+	vdev->config->del_vqs(vdev);
+
+	return ret;
+}
+
+static void viommu_remove(struct virtio_device *vdev)
+{
+	struct viommu_dev *viommu = vdev->priv;
+
+	iommu_device_sysfs_remove(&viommu->iommu);
+	iommu_device_unregister(&viommu->iommu);
+
+	/* Stop all virtqueues */
+	vdev->config->reset(vdev);
+	vdev->config->del_vqs(vdev);
+
+	dev_info(&vdev->dev, "device removed\n");
+}
+
+static void viommu_config_changed(struct virtio_device *vdev)
+{
+	dev_warn(&vdev->dev, "config changed\n");
+}
+
+static unsigned int features[] = {
+	VIRTIO_IOMMU_F_MAP_UNMAP,
+	VIRTIO_IOMMU_F_DOMAIN_BITS,
+	VIRTIO_IOMMU_F_INPUT_RANGE,
+};
+
+static struct virtio_device_id id_table[] = {
+	{ VIRTIO_ID_IOMMU, VIRTIO_DEV_ANY_ID },
+	{ 0 },
+};
+
+static struct virtio_driver virtio_iommu_drv = {
+	.driver.name		= KBUILD_MODNAME,
+	.driver.owner		= THIS_MODULE,
+	.id_table		= id_table,
+	.feature_table		= features,
+	.feature_table_size	= ARRAY_SIZE(features),
+	.probe			= viommu_probe,
+	.remove			= viommu_remove,
+	.config_changed		= viommu_config_changed,
+};
+
+module_virtio_driver(virtio_iommu_drv);
+
+MODULE_DESCRIPTION("Virtio IOMMU driver");
+MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>");
+MODULE_LICENSE("GPL v2");
diff --git a/include/uapi/linux/virtio_ids.h b/include/uapi/linux/virtio_ids.h
index 6d5c3b2d4f4d..cfe47c5d9a56 100644
--- a/include/uapi/linux/virtio_ids.h
+++ b/include/uapi/linux/virtio_ids.h
@@ -43,5 +43,6 @@
 #define VIRTIO_ID_INPUT        18 /* virtio input */
 #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
 #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
+#define VIRTIO_ID_IOMMU        23 /* virtio IOMMU */
 
 #endif /* _LINUX_VIRTIO_IDS_H */
diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
new file mode 100644
index 000000000000..2e0bf5792f26
--- /dev/null
+++ b/include/uapi/linux/virtio_iommu.h
@@ -0,0 +1,104 @@
+/* SPDX-License-Identifier: BSD-3-Clause */
+/*
+ * Virtio-iommu definition v0.8
+ *
+ * Copyright (C) 2018 Arm Ltd.
+ */
+#ifndef _UAPI_LINUX_VIRTIO_IOMMU_H
+#define _UAPI_LINUX_VIRTIO_IOMMU_H
+
+#include <linux/types.h>
+
+/* Feature bits */
+#define VIRTIO_IOMMU_F_INPUT_RANGE		0
+#define VIRTIO_IOMMU_F_DOMAIN_BITS		1
+#define VIRTIO_IOMMU_F_MAP_UNMAP		2
+#define VIRTIO_IOMMU_F_BYPASS			3
+
+struct virtio_iommu_range {
+	__u64					start;
+	__u64					end;
+};
+
+struct virtio_iommu_config {
+	/* Supported page sizes */
+	__u64					page_size_mask;
+	/* Supported IOVA range */
+	struct virtio_iommu_range		input_range;
+	/* Max domain ID size */
+	__u8					domain_bits;
+	__u8					padding[3];
+};
+
+/* Request types */
+#define VIRTIO_IOMMU_T_ATTACH			0x01
+#define VIRTIO_IOMMU_T_DETACH			0x02
+#define VIRTIO_IOMMU_T_MAP			0x03
+#define VIRTIO_IOMMU_T_UNMAP			0x04
+
+/* Status types */
+#define VIRTIO_IOMMU_S_OK			0x00
+#define VIRTIO_IOMMU_S_IOERR			0x01
+#define VIRTIO_IOMMU_S_UNSUPP			0x02
+#define VIRTIO_IOMMU_S_DEVERR			0x03
+#define VIRTIO_IOMMU_S_INVAL			0x04
+#define VIRTIO_IOMMU_S_RANGE			0x05
+#define VIRTIO_IOMMU_S_NOENT			0x06
+#define VIRTIO_IOMMU_S_FAULT			0x07
+
+struct virtio_iommu_req_head {
+	__u8					type;
+	__u8					reserved[3];
+};
+
+struct virtio_iommu_req_tail {
+	__u8					status;
+	__u8					reserved[3];
+};
+
+struct virtio_iommu_req_attach {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le32					endpoint;
+	__u8					reserved[8];
+	struct virtio_iommu_req_tail		tail;
+};
+
+struct virtio_iommu_req_detach {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le32					endpoint;
+	__u8					reserved[8];
+	struct virtio_iommu_req_tail		tail;
+};
+
+#define VIRTIO_IOMMU_MAP_F_READ			(1 << 0)
+#define VIRTIO_IOMMU_MAP_F_WRITE		(1 << 1)
+#define VIRTIO_IOMMU_MAP_F_EXEC			(1 << 2)
+#define VIRTIO_IOMMU_MAP_F_MMIO			(1 << 3)
+
+#define VIRTIO_IOMMU_MAP_F_MASK			(VIRTIO_IOMMU_MAP_F_READ |	\
+						 VIRTIO_IOMMU_MAP_F_WRITE |	\
+						 VIRTIO_IOMMU_MAP_F_EXEC |	\
+						 VIRTIO_IOMMU_MAP_F_MMIO)
+
+struct virtio_iommu_req_map {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le64					virt_start;
+	__le64					virt_end;
+	__le64					phys_start;
+	__le32					flags;
+	struct virtio_iommu_req_tail		tail;
+};
+
+struct virtio_iommu_req_unmap {
+	struct virtio_iommu_req_head		head;
+	__le32					domain;
+	__le64					virt_start;
+	__le64					virt_end;
+	__u8					reserved[4];
+	struct virtio_iommu_req_tail		tail;
+};
+
+#endif
-- 
2.19.1

When the device offers the probe feature, send a probe request for each
device managed by the IOMMU. Extract RESV_MEM information. When we
encounter a MSI doorbell region, set it up as a IOMMU_RESV_MSI region.
This will tell other subsystems that there is no need to map the MSI
doorbell in the virtio-iommu, because MSIs bypass it.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 drivers/iommu/virtio-iommu.c      | 156 ++++++++++++++++++++++++++++--
 include/uapi/linux/virtio_iommu.h |  38 ++++++++
 2 files changed, 188 insertions(+), 6 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index 2a9cb6285a1e..c547ebd79c43 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -46,6 +46,7 @@ struct viommu_dev {
 	struct iommu_domain_geometry	geometry;
 	u64				pgsize_bitmap;
 	u8				domain_bits;
+	u32				probe_size;
 };
 
 struct viommu_mapping {
@@ -67,8 +68,10 @@ struct viommu_domain {
 };
 
 struct viommu_endpoint {
+	struct device			*dev;
 	struct viommu_dev		*viommu;
 	struct viommu_domain		*vdomain;
+	struct list_head		resv_regions;
 };
 
 struct viommu_request {
@@ -119,6 +122,9 @@ static off_t viommu_get_req_offset(struct viommu_dev
*viommu,
 {
 	size_t tail_size = sizeof(struct virtio_iommu_req_tail);
 
+	if (req->type == VIRTIO_IOMMU_T_PROBE)
+		return len - viommu->probe_size - tail_size;
+
 	return len - tail_size;
 }
 
@@ -394,6 +400,110 @@ static int viommu_replay_mappings(struct viommu_domain
*vdomain)
 	return ret;
 }
 
+static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
+			       struct virtio_iommu_probe_resv_mem *mem,
+			       size_t len)
+{
+	size_t size;
+	u64 start64, end64;
+	phys_addr_t start, end;
+	struct iommu_resv_region *region = NULL;
+	unsigned long prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
+
+	start = start64 = le64_to_cpu(mem->start);
+	end = end64 = le64_to_cpu(mem->end);
+	size = end64 - start64 + 1;
+
+	/* Catch any overflow, including the unlikely end64 - start64 + 1 = 0 */
+	if (start != start64 || end != end64 || size < end64 - start64)
+		return -EOVERFLOW;
+
+	if (len < sizeof(*mem))
+		return -EINVAL;
+
+	switch (mem->subtype) {
+	default:
+		dev_warn(vdev->dev, "unknown resv mem subtype 0x%x\n",
+			 mem->subtype);
+		/* Fall-through */
+	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
+		region = iommu_alloc_resv_region(start, size, 0,
+						 IOMMU_RESV_RESERVED);
+		break;
+	case VIRTIO_IOMMU_RESV_MEM_T_MSI:
+		region = iommu_alloc_resv_region(start, size, prot,
+						 IOMMU_RESV_MSI);
+		break;
+	}
+	if (!region)
+		return -ENOMEM;
+
+	list_add(&vdev->resv_regions, &region->list);
+	return 0;
+}
+
+static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device *dev)
+{
+	int ret;
+	u16 type, len;
+	size_t cur = 0;
+	size_t probe_len;
+	struct virtio_iommu_req_probe *probe;
+	struct virtio_iommu_probe_property *prop;
+	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
+	struct viommu_endpoint *vdev = fwspec->iommu_priv;
+
+	if (!fwspec->num_ids)
+		return -EINVAL;
+
+	probe_len = sizeof(*probe) + viommu->probe_size +
+		    sizeof(struct virtio_iommu_req_tail);
+	probe = kzalloc(probe_len, GFP_KERNEL);
+	if (!probe)
+		return -ENOMEM;
+
+	probe->head.type = VIRTIO_IOMMU_T_PROBE;
+	/*
+	 * For now, assume that properties of an endpoint that outputs multiple
+	 * IDs are consistent. Only probe the first one.
+	 */
+	probe->endpoint = cpu_to_le32(fwspec->ids[0]);
+
+	ret = viommu_send_req_sync(viommu, probe, probe_len);
+	if (ret)
+		goto out_free;
+
+	prop = (void *)probe->properties;
+	type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
+
+	while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
+	       cur < viommu->probe_size) {
+		len = le16_to_cpu(prop->length) + sizeof(*prop);
+
+		switch (type) {
+		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
+			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
+			break;
+		default:
+			dev_err(dev, "unknown viommu prop 0x%x\n", type);
+		}
+
+		if (ret)
+			dev_err(dev, "failed to parse viommu prop 0x%x\n", type);
+
+		cur += len;
+		if (cur >= viommu->probe_size)
+			break;
+
+		prop = (void *)probe->properties + cur;
+		type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
+	}
+
+out_free:
+	kfree(probe);
+	return ret;
+}
+
 /* IOMMU API */
 
 static struct iommu_domain *viommu_domain_alloc(unsigned type)
@@ -616,15 +726,33 @@ static void viommu_iotlb_sync(struct iommu_domain *domain)
 
 static void viommu_get_resv_regions(struct device *dev, struct list_head *head)
 {
-	struct iommu_resv_region *region;
+	struct iommu_resv_region *entry, *new_entry, *msi = NULL;
+	struct viommu_endpoint *vdev = dev->iommu_fwspec->iommu_priv;
 	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
 
-	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
-					 IOMMU_RESV_SW_MSI);
-	if (!region)
-		return;
+	list_for_each_entry(entry, &vdev->resv_regions, list) {
+		if (entry->type == IOMMU_RESV_MSI)
+			msi = entry;
+
+		new_entry = kmemdup(entry, sizeof(*entry), GFP_KERNEL);
+		if (!new_entry)
+			return;
+		list_add_tail(&new_entry->list, head);
+	}
+
+	/*
+	 * If the device didn't register any bypass MSI window, add a
+	 * software-mapped region.
+	 */
+	if (!msi) {
+		msi = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
+					      prot, IOMMU_RESV_SW_MSI);
+		if (!msi)
+			return;
+
+		list_add_tail(&msi->list, head);
+	}
 
-	list_add_tail(&region->list, head);
 	iommu_dma_get_resv_regions(dev, head);
 }
 
@@ -672,9 +800,18 @@ static int viommu_add_device(struct device *dev)
 	if (!vdev)
 		return -ENOMEM;
 
+	vdev->dev = dev;
 	vdev->viommu = viommu;
+	INIT_LIST_HEAD(&vdev->resv_regions);
 	fwspec->iommu_priv = vdev;
 
+	if (viommu->probe_size) {
+		/* Get additional information for this endpoint */
+		ret = viommu_probe_endpoint(viommu, dev);
+		if (ret)
+			goto err_free_dev;
+	}
+
 	ret = iommu_device_link(&viommu->iommu, dev);
 	if (ret)
 		goto err_free_dev;
@@ -696,6 +833,7 @@ static int viommu_add_device(struct device *dev)
 err_unlink_dev:
 	iommu_device_unlink(&viommu->iommu, dev);
 err_free_dev:
+	viommu_put_resv_regions(dev, &vdev->resv_regions);
 	kfree(vdev);
 
 	return ret;
@@ -713,6 +851,7 @@ static void viommu_remove_device(struct device *dev)
 
 	iommu_group_remove_device(dev);
 	iommu_device_unlink(&vdev->viommu->iommu, dev);
+	viommu_put_resv_regions(dev, &vdev->resv_regions);
 	kfree(vdev);
 }
 
@@ -812,6 +951,10 @@ static int viommu_probe(struct virtio_device *vdev)
 			     struct virtio_iommu_config, domain_bits,
 			     &viommu->domain_bits);
 
+	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_PROBE,
+			     struct virtio_iommu_config, probe_size,
+			     &viommu->probe_size);
+
 	viommu->geometry = (struct iommu_domain_geometry) {
 		.aperture_start	= input_start,
 		.aperture_end	= input_end,
@@ -893,6 +1036,7 @@ static unsigned int features[] = {
 	VIRTIO_IOMMU_F_MAP_UNMAP,
 	VIRTIO_IOMMU_F_DOMAIN_BITS,
 	VIRTIO_IOMMU_F_INPUT_RANGE,
+	VIRTIO_IOMMU_F_PROBE,
 };
 
 static struct virtio_device_id id_table[] = {
diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
index 2e0bf5792f26..cde2a3409caa 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -14,6 +14,7 @@
 #define VIRTIO_IOMMU_F_DOMAIN_BITS		1
 #define VIRTIO_IOMMU_F_MAP_UNMAP		2
 #define VIRTIO_IOMMU_F_BYPASS			3
+#define VIRTIO_IOMMU_F_PROBE			4
 
 struct virtio_iommu_range {
 	__u64					start;
@@ -28,6 +29,8 @@ struct virtio_iommu_config {
 	/* Max domain ID size */
 	__u8					domain_bits;
 	__u8					padding[3];
+	/* Probe buffer size */
+	__u32					probe_size;
 };
 
 /* Request types */
@@ -35,6 +38,7 @@ struct virtio_iommu_config {
 #define VIRTIO_IOMMU_T_DETACH			0x02
 #define VIRTIO_IOMMU_T_MAP			0x03
 #define VIRTIO_IOMMU_T_UNMAP			0x04
+#define VIRTIO_IOMMU_T_PROBE			0x05
 
 /* Status types */
 #define VIRTIO_IOMMU_S_OK			0x00
@@ -101,4 +105,38 @@ struct virtio_iommu_req_unmap {
 	struct virtio_iommu_req_tail		tail;
 };
 
+#define VIRTIO_IOMMU_PROBE_T_NONE		0
+#define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
+
+#define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
+
+struct virtio_iommu_probe_property {
+	__le16					type;
+	__le16					length;
+};
+
+#define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
+#define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
+
+struct virtio_iommu_probe_resv_mem {
+	struct virtio_iommu_probe_property	head;
+	__u8					subtype;
+	__u8					reserved[3];
+	__le64					start;
+	__le64					end;
+};
+
+struct virtio_iommu_req_probe {
+	struct virtio_iommu_req_head		head;
+	__le32					endpoint;
+	__u8					reserved[64];
+
+	__u8					properties[];
+
+	/*
+	 * Tail follows the variable-length properties array. No padding,
+	 * property lengths are all aligned on 8 bytes.
+	 */
+};
+
 #endif
-- 
2.19.1

The event queue offers a way for the device to report access faults from
endpoints. It is implemented on virtqueue #1. Whenever the host needs to
signal a fault, it fills one of the buffers offered by the guest and
interrupts it.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
---
 drivers/iommu/virtio-iommu.c      | 116 +++++++++++++++++++++++++++---
 include/uapi/linux/virtio_iommu.h |  19 +++++
 2 files changed, 126 insertions(+), 9 deletions(-)

diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index c547ebd79c43..81c6b72e9c43 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -29,7 +29,8 @@
 #define MSI_IOVA_LENGTH			0x100000
 
 #define VIOMMU_REQUEST_VQ		0
-#define VIOMMU_NR_VQS			1
+#define VIOMMU_EVENT_VQ			1
+#define VIOMMU_NR_VQS			2
 
 struct viommu_dev {
 	struct iommu_device		iommu;
@@ -41,6 +42,7 @@ struct viommu_dev {
 	struct virtqueue		*vqs[VIOMMU_NR_VQS];
 	spinlock_t			request_lock;
 	struct list_head		requests;
+	void				*evts;
 
 	/* Device configuration */
 	struct iommu_domain_geometry	geometry;
@@ -82,6 +84,15 @@ struct viommu_request {
 	char				buf[];
 };
 
+#define VIOMMU_FAULT_RESV_MASK		0xffffff00
+
+struct viommu_event {
+	union {
+		u32			head;
+		struct virtio_iommu_fault fault;
+	};
+};
+
 #define to_viommu_domain(domain)	\
 	container_of(domain, struct viommu_domain, domain)
 
@@ -504,6 +515,69 @@ static int viommu_probe_endpoint(struct viommu_dev *viommu,
struct device *dev)
 	return ret;
 }
 
+static int viommu_fault_handler(struct viommu_dev *viommu,
+				struct virtio_iommu_fault *fault)
+{
+	char *reason_str;
+
+	u8 reason	= fault->reason;
+	u32 flags	= le32_to_cpu(fault->flags);
+	u32 endpoint	= le32_to_cpu(fault->endpoint);
+	u64 address	= le64_to_cpu(fault->address);
+
+	switch (reason) {
+	case VIRTIO_IOMMU_FAULT_R_DOMAIN:
+		reason_str = "domain";
+		break;
+	case VIRTIO_IOMMU_FAULT_R_MAPPING:
+		reason_str = "page";
+		break;
+	case VIRTIO_IOMMU_FAULT_R_UNKNOWN:
+	default:
+		reason_str = "unknown";
+		break;
+	}
+
+	/* TODO: find EP by ID and report_iommu_fault */
+	if (flags & VIRTIO_IOMMU_FAULT_F_ADDRESS)
+		dev_err_ratelimited(viommu->dev, "%s fault from EP %u at %#llx
[%s%s%s]\n",
+				    reason_str, endpoint, address,
+				    flags & VIRTIO_IOMMU_FAULT_F_READ ? "R" : "",
+				    flags & VIRTIO_IOMMU_FAULT_F_WRITE ? "W" : "",
+				    flags & VIRTIO_IOMMU_FAULT_F_EXEC ? "X" : "");
+	else
+		dev_err_ratelimited(viommu->dev, "%s fault from EP %u\n",
+				    reason_str, endpoint);
+	return 0;
+}
+
+static void viommu_event_handler(struct virtqueue *vq)
+{
+	int ret;
+	unsigned int len;
+	struct scatterlist sg[1];
+	struct viommu_event *evt;
+	struct viommu_dev *viommu = vq->vdev->priv;
+
+	while ((evt = virtqueue_get_buf(vq, &len)) != NULL) {
+		if (len > sizeof(*evt)) {
+			dev_err(viommu->dev,
+				"invalid event buffer (len %u != %zu)\n",
+				len, sizeof(*evt));
+		} else if (!(evt->head & VIOMMU_FAULT_RESV_MASK)) {
+			viommu_fault_handler(viommu, &evt->fault);
+		}
+
+		sg_init_one(sg, evt, sizeof(*evt));
+		ret = virtqueue_add_inbuf(vq, sg, 1, evt, GFP_ATOMIC);
+		if (ret)
+			dev_err(viommu->dev, "could not add event buffer\n");
+	}
+
+	if (!virtqueue_kick(vq))
+		dev_err(viommu->dev, "kick failed\n");
+}
+
 /* IOMMU API */
 
 static struct iommu_domain *viommu_domain_alloc(unsigned type)
@@ -887,16 +961,35 @@ static struct iommu_ops viommu_ops = {
 static int viommu_init_vqs(struct viommu_dev *viommu)
 {
 	struct virtio_device *vdev = dev_to_virtio(viommu->dev);
-	const char *name = "request";
-	void *ret;
+	const char *names[] = { "request", "event" };
+	vq_callback_t *callbacks[] = {
+		NULL, /* No async requests */
+		viommu_event_handler,
+	};
 
-	ret = virtio_find_single_vq(vdev, NULL, name);
-	if (IS_ERR(ret)) {
-		dev_err(viommu->dev, "cannot find VQ\n");
-		return PTR_ERR(ret);
-	}
+	return virtio_find_vqs(vdev, VIOMMU_NR_VQS, viommu->vqs, callbacks,
+			       names, NULL);
+}
 
-	viommu->vqs[VIOMMU_REQUEST_VQ] = ret;
+static int viommu_fill_evtq(struct viommu_dev *viommu)
+{
+	int i, ret;
+	struct scatterlist sg[1];
+	struct viommu_event *evts;
+	struct virtqueue *vq = viommu->vqs[VIOMMU_EVENT_VQ];
+	size_t nr_evts = vq->num_free;
+
+	viommu->evts = evts = devm_kmalloc_array(viommu->dev, nr_evts,
+						 sizeof(*evts), GFP_KERNEL);
+	if (!evts)
+		return -ENOMEM;
+
+	for (i = 0; i < nr_evts; i++) {
+		sg_init_one(sg, &evts[i], sizeof(*evts));
+		ret = virtqueue_add_inbuf(vq, sg, 1, &evts[i], GFP_KERNEL);
+		if (ret)
+			return ret;
+	}
 
 	return 0;
 }
@@ -965,6 +1058,11 @@ static int viommu_probe(struct virtio_device *vdev)
 
 	virtio_device_ready(vdev);
 
+	/* Populate the event queue with buffers */
+	ret = viommu_fill_evtq(viommu);
+	if (ret)
+		goto err_free_vqs;
+
 	ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL, "%s",
 				     virtio_bus_name(vdev));
 	if (ret)
diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
index cde2a3409caa..fed2ba5b47ab 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -139,4 +139,23 @@ struct virtio_iommu_req_probe {
 	 */
 };
 
+/* Fault types */
+#define VIRTIO_IOMMU_FAULT_R_UNKNOWN		0
+#define VIRTIO_IOMMU_FAULT_R_DOMAIN		1
+#define VIRTIO_IOMMU_FAULT_R_MAPPING		2
+
+#define VIRTIO_IOMMU_FAULT_F_READ		(1 << 0)
+#define VIRTIO_IOMMU_FAULT_F_WRITE		(1 << 1)
+#define VIRTIO_IOMMU_FAULT_F_EXEC		(1 << 2)
+#define VIRTIO_IOMMU_FAULT_F_ADDRESS		(1 << 8)
+
+struct virtio_iommu_fault {
+	__u8					reason;
+	__u8					reserved[3];
+	__le32					flags;
+	__le32					endpoint;
+	__u8					reserved2[4];
+	__le64					address;
+};
+
 #endif
-- 
2.19.1

Hi Jean,

On 11/15/18 5:52 PM, Jean-Philippe Brucker wrote:
> The virtio IOMMU is a para-virtualized device, allowing to send IOMMU
> requests such as map/unmap over virtio transport without emulating page
> tables. This implementation handles ATTACH, DETACH, MAP and UNMAP
> requests.
> 
> The bulk of the code transforms calls coming from the IOMMU API into
> corresponding virtio requests. Mappings are kept in an interval tree
> instead of page tables.
Some few comments/questions below.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>
> ---
>  MAINTAINERS                       |   7 +
>  drivers/iommu/Kconfig             |  11 +
>  drivers/iommu/Makefile            |   1 +
>  drivers/iommu/virtio-iommu.c      | 918 ++++++++++++++++++++++++++++++
>  include/uapi/linux/virtio_ids.h   |   1 +
>  include/uapi/linux/virtio_iommu.h | 104 ++++
>  6 files changed, 1042 insertions(+)
>  create mode 100644 drivers/iommu/virtio-iommu.c
>  create mode 100644 include/uapi/linux/virtio_iommu.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 0abecc528dac..0c7bdce57719 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -15948,6 +15948,13 @@ S:	Maintained
>  F:	drivers/virtio/virtio_input.c
>  F:	include/uapi/linux/virtio_input.h
>  
> +VIRTIO IOMMU DRIVER
> +M:	Jean-Philippe Brucker <jean-philippe.brucker at arm.com>
> +L:	virtualization at lists.linux-foundation.org
> +S:	Maintained
> +F:	drivers/iommu/virtio-iommu.c
> +F:	include/uapi/linux/virtio_iommu.h
> +
>  VIRTUAL BOX GUEST DEVICE DRIVER
>  M:	Hans de Goede <hdegoede at redhat.com>
>  M:	Arnd Bergmann <arnd at arndb.de>
> diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
> index d9a25715650e..efdeaaeee0e0 100644
> --- a/drivers/iommu/Kconfig
> +++ b/drivers/iommu/Kconfig
> @@ -435,4 +435,15 @@ config QCOM_IOMMU
>  	help
>  	  Support for IOMMU on certain Qualcomm SoCs.
>  
> +config VIRTIO_IOMMU
> +	bool "Virtio IOMMU driver"
> +	depends on VIRTIO=y
> +	select IOMMU_API
> +	select INTERVAL_TREE
> +	select ARM_DMA_USE_IOMMU if ARM
> +	help
> +	  Para-virtualised IOMMU driver with virtio.
> +
> +	  Say Y here if you intend to run this kernel as a guest.
> +
>  endif # IOMMU_SUPPORT
> diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
> index a158a68c8ea8..48d831a39281 100644
> --- a/drivers/iommu/Makefile
> +++ b/drivers/iommu/Makefile
> @@ -32,3 +32,4 @@ obj-$(CONFIG_EXYNOS_IOMMU) += exynos-iommu.o
>  obj-$(CONFIG_FSL_PAMU) += fsl_pamu.o fsl_pamu_domain.o
>  obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
>  obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
> +obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> new file mode 100644
> index 000000000000..2a9cb6285a1e
> --- /dev/null
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -0,0 +1,918 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Virtio driver for the paravirtualized IOMMU
> + *
> + * Copyright (C) 2018 Arm Limited
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/amba/bus.h>
> +#include <linux/delay.h>
> +#include <linux/dma-iommu.h>
> +#include <linux/freezer.h>
> +#include <linux/interval_tree.h>
> +#include <linux/iommu.h>
> +#include <linux/module.h>
> +#include <linux/of_iommu.h>
> +#include <linux/of_platform.h>
> +#include <linux/pci.h>
> +#include <linux/platform_device.h>
> +#include <linux/virtio.h>
> +#include <linux/virtio_config.h>
> +#include <linux/virtio_ids.h>
> +#include <linux/wait.h>
> +
> +#include <uapi/linux/virtio_iommu.h>
> +
> +#define MSI_IOVA_BASE			0x8000000
> +#define MSI_IOVA_LENGTH			0x100000
> +
> +#define VIOMMU_REQUEST_VQ		0
> +#define VIOMMU_NR_VQS			1
> +
> +struct viommu_dev {
> +	struct iommu_device		iommu;
> +	struct device			*dev;
> +	struct virtio_device		*vdev;
> +
> +	struct ida			domain_ids;
> +
> +	struct virtqueue		*vqs[VIOMMU_NR_VQS];
> +	spinlock_t			request_lock;
> +	struct list_head		requests;
> +
> +	/* Device configuration */
> +	struct iommu_domain_geometry	geometry;
> +	u64				pgsize_bitmap;
> +	u8				domain_bits;
> +};
> +
> +struct viommu_mapping {
> +	phys_addr_t			paddr;
> +	struct interval_tree_node	iova;
> +	u32				flags;
> +};
> +
> +struct viommu_domain {
> +	struct iommu_domain		domain;
> +	struct viommu_dev		*viommu;
> +	struct mutex			mutex;
same naming/comment as in smmu driver may help here
struct mutex                 init_mutex; /* Protects viommu pointer
*/
> +	unsigned int			id;
> +
> +	spinlock_t			mappings_lock;
> +	struct rb_root_cached		mappings;
> +
> +	unsigned long			nr_endpoints;
> +};
> +
> +struct viommu_endpoint {
> +	struct viommu_dev		*viommu;
> +	struct viommu_domain		*vdomain;
> +};
> +
> +struct viommu_request {
> +	struct list_head		list;
> +	void				*writeback;
> +	unsigned int			write_offset;
> +	unsigned int			len;
> +	char				buf[];
> +};
> +
> +#define to_viommu_domain(domain)	\
> +	container_of(domain, struct viommu_domain, domain)
> +
> +static int viommu_get_req_errno(void *buf, size_t len)
> +{
> +	struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);
> +
> +	switch (tail->status) {
> +	case VIRTIO_IOMMU_S_OK:
> +		return 0;
> +	case VIRTIO_IOMMU_S_UNSUPP:
> +		return -ENOSYS;
> +	case VIRTIO_IOMMU_S_INVAL:
> +		return -EINVAL;
> +	case VIRTIO_IOMMU_S_RANGE:
> +		return -ERANGE;
> +	case VIRTIO_IOMMU_S_NOENT:
> +		return -ENOENT;
> +	case VIRTIO_IOMMU_S_FAULT:
> +		return -EFAULT;
> +	case VIRTIO_IOMMU_S_IOERR:
> +	case VIRTIO_IOMMU_S_DEVERR:
> +	default:
> +		return -EIO;
> +	}
> +}
> +
> +static void viommu_set_req_status(void *buf, size_t len, int status)
> +{
> +	struct virtio_iommu_req_tail *tail = buf + len - sizeof(*tail);
> +
> +	tail->status = status;
> +}
> +
> +static off_t viommu_get_req_offset(struct viommu_dev *viommu,
> +				   struct virtio_iommu_req_head *req,
> +				   size_t len)
nit: viommu_get_write_desc_offset would be more
self-explanatory?
> +{
> +	size_t tail_size = sizeof(struct virtio_iommu_req_tail);
> +
> +	return len - tail_size;
> +}
> +
> +/*
> + * __viommu_sync_req - Complete all in-flight requests
> + *
> + * Wait for all added requests to complete. When this function returns,
all
> + * requests that were in-flight at the time of the call have completed.
> + */
> +static int __viommu_sync_req(struct viommu_dev *viommu)
> +{
> +	int ret = 0;
> +	unsigned int len;
> +	size_t write_len;
> +	struct viommu_request *req;
> +	struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];
> +
> +	assert_spin_locked(&viommu->request_lock);
> +
> +	virtqueue_kick(vq);
> +
> +	while (!list_empty(&viommu->requests)) {
> +		len = 0;
> +		req = virtqueue_get_buf(vq, &len);
> +		if (!req)
> +			continue;
> +
> +		if (!len)
> +			viommu_set_req_status(req->buf, req->len,
> +					      VIRTIO_IOMMU_S_IOERR);
> +
> +		write_len = req->len - req->write_offset;
> +		if (req->writeback && len >= write_len)
I don't get "len >= write_len". Is it valid for the device to
write more
than write_len? If it writes less than write_len, the status is not set,
is it?
> +			memcpy(req->writeback, req->buf + req->write_offset,
> +			       write_len);
> +
> +		list_del(&req->list);
> +		kfree(req);
> +	}
> +
> +	return ret;
> +}
> +
> +static int viommu_sync_req(struct viommu_dev *viommu)
> +{
> +	int ret;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&viommu->request_lock, flags);
> +	ret = __viommu_sync_req(viommu);
> +	if (ret)
> +		dev_dbg(viommu->dev, "could not sync requests (%d)\n",
ret);
> +	spin_unlock_irqrestore(&viommu->request_lock, flags);
> +
> +	return ret;
> +}
> +
> +/*
> + * __viommu_add_request - Add one request to the queue
> + * @buf: pointer to the request buffer
> + * @len: length of the request buffer
> + * @writeback: copy data back to the buffer when the request completes.
> + *
> + * Add a request to the queue. Only synchronize the queue if it's
already full.
> + * Otherwise don't kick the queue nor wait for requests to complete.
> + *
> + * When @writeback is true, data written by the device, including the
request
> + * status, is copied into @buf after the request completes. This is unsafe
if
> + * the caller allocates @buf on stack and drops the lock between add_req()
and
> + * sync_req().
> + *
> + * Return 0 if the request was successfully added to the queue.
> + */
> +static int __viommu_add_req(struct viommu_dev *viommu, void *buf, size_t
len,
> +			    bool writeback)
> +{
> +	int ret;
> +	off_t write_offset;
> +	struct viommu_request *req;
> +	struct scatterlist top_sg, bottom_sg;
> +	struct scatterlist *sg[2] = { &top_sg, &bottom_sg };
> +	struct virtqueue *vq = viommu->vqs[VIOMMU_REQUEST_VQ];
> +
> +	assert_spin_locked(&viommu->request_lock);
> +
> +	write_offset = viommu_get_req_offset(viommu, buf, len);
> +	if (!write_offset)
could be < 0 as well?
> +		return -EINVAL;
> +
> +	req = kzalloc(sizeof(*req) + len, GFP_ATOMIC);
> +	if (!req)
> +		return -ENOMEM;
> +
> +	req->len = len;
> +	if (writeback) {
> +		req->writeback = buf + write_offset;
> +		req->write_offset = write_offset;
> +	}
> +	memcpy(&req->buf, buf, write_offset);
> +
> +	sg_init_one(&top_sg, req->buf, write_offset);
> +	sg_init_one(&bottom_sg, req->buf + write_offset, len -
write_offset);
> +
> +	ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
> +	if (ret == -ENOSPC) {
> +		/* If the queue is full, sync and retry */
> +		if (!__viommu_sync_req(viommu))
> +			ret = virtqueue_add_sgs(vq, sg, 1, 1, req, GFP_ATOMIC);
> +	}
> +	if (ret)
> +		goto err_free;
> +
> +	list_add_tail(&req->list, &viommu->requests);
> +	return 0;
> +
> +err_free:
> +	kfree(req);
> +	return ret;
> +}
> +
> +static int viommu_add_req(struct viommu_dev *viommu, void *buf, size_t
len)
> +{
> +	int ret;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&viommu->request_lock, flags);
> +	ret = __viommu_add_req(viommu, buf, len, false);
> +	if (ret)
> +		dev_dbg(viommu->dev, "could not add request: %d\n", ret);
> +	spin_unlock_irqrestore(&viommu->request_lock, flags);
> +
> +	return ret;
> +}
> +
> +/*
> + * Send a request and wait for it to complete. Return the request status
(as an
> + * errno)
> + */
> +static int viommu_send_req_sync(struct viommu_dev *viommu, void *buf,
> +				size_t len)
> +{
> +	int ret;
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&viommu->request_lock, flags);
> +
> +	ret = __viommu_add_req(viommu, buf, len, true);
> +	if (ret) {
> +		dev_dbg(viommu->dev, "could not add request (%d)\n", ret);
> +		goto out_unlock;
> +	}
> +
> +	ret = __viommu_sync_req(viommu);
> +	if (ret) {
> +		dev_dbg(viommu->dev, "could not sync requests (%d)\n",
ret);
> +		/* Fall-through (get the actual request status) */
> +	}
> +
> +	ret = viommu_get_req_errno(buf, len);
> +out_unlock:
> +	spin_unlock_irqrestore(&viommu->request_lock, flags);
> +	return ret;
> +}
> +
> +/*
> + * viommu_add_mapping - add a mapping to the internal tree
> + *
> + * On success, return the new mapping. Otherwise return NULL.
> + */
> +static struct viommu_mapping *
> +viommu_add_mapping(struct viommu_domain *vdomain, unsigned long iova,
> +		   phys_addr_t paddr, size_t size, u32 flags)
> +{
> +	unsigned long irqflags;
> +	struct viommu_mapping *mapping;
> +
> +	mapping = kzalloc(sizeof(*mapping), GFP_ATOMIC);
> +	if (!mapping)
> +		return NULL;
> +
> +	mapping->paddr		= paddr;
> +	mapping->iova.start	= iova;
> +	mapping->iova.last	= iova + size - 1;
> +	mapping->flags		= flags;
> +
> +	spin_lock_irqsave(&vdomain->mappings_lock, irqflags);
> +	interval_tree_insert(&mapping->iova, &vdomain->mappings);
> +	spin_unlock_irqrestore(&vdomain->mappings_lock, irqflags);
> +
> +	return mapping;
> +}
> +
> +/*
> + * viommu_del_mappings - remove mappings from the internal tree
> + *
> + * @vdomain: the domain
> + * @iova: start of the range
> + * @size: size of the range. A size of 0 corresponds to the entire address
> + *	space.
> + *
> + * On success, returns the number of unmapped bytes (>= size)
> + */
> +static size_t viommu_del_mappings(struct viommu_domain *vdomain,
> +				  unsigned long iova, size_t size)
> +{
> +	size_t unmapped = 0;
> +	unsigned long flags;
> +	unsigned long last = iova + size - 1;
> +	struct viommu_mapping *mapping = NULL;
> +	struct interval_tree_node *node, *next;
> +
> +	spin_lock_irqsave(&vdomain->mappings_lock, flags);
> +	next = interval_tree_iter_first(&vdomain->mappings, iova, last);
> +	while (next) {
> +		node = next;
> +		mapping = container_of(node, struct viommu_mapping, iova);
> +		next = interval_tree_iter_next(node, iova, last);
> +
> +		/* Trying to split a mapping? */
> +		if (mapping->iova.start < iova)
> +			break;
> +
> +		/*
> +		 * Note that for a partial range, this will return the full
> +		 * mapping so we avoid sending split requests to the device.
> +		 */
This comment is not crystal clear to me, ie. why do we remove the entire
node even if @size is less than mapping->iova.last - mapping->iova.start
+ 1.
> +		unmapped += mapping->iova.last - mapping->iova.start + 1;
> +
> +		interval_tree_remove(node, &vdomain->mappings);
> +		kfree(mapping);
> +	}
> +	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
> +
> +	return unmapped;
> +}
> +
> +/*
> + * viommu_replay_mappings - re-send MAP requests
> + *
> + * When reattaching a domain that was previously detached from all
endpoints,
> + * mappings were deleted from the device. Re-create the mappings available
in
> + * the internal tree.
> + */
> +static int viommu_replay_mappings(struct viommu_domain *vdomain)
> +{
> +	int ret = 0;
> +	unsigned long flags;
> +	struct viommu_mapping *mapping;
> +	struct interval_tree_node *node;
> +	struct virtio_iommu_req_map map;
> +
> +	spin_lock_irqsave(&vdomain->mappings_lock, flags);
> +	node = interval_tree_iter_first(&vdomain->mappings, 0, -1UL);
> +	while (node) {
> +		mapping = container_of(node, struct viommu_mapping, iova);
> +		map = (struct virtio_iommu_req_map) {
> +			.head.type	= VIRTIO_IOMMU_T_MAP,
> +			.domain		= cpu_to_le32(vdomain->id),
> +			.virt_start	= cpu_to_le64(mapping->iova.start),
> +			.virt_end	= cpu_to_le64(mapping->iova.last),
> +			.phys_start	= cpu_to_le64(mapping->paddr),
> +			.flags		= cpu_to_le32(mapping->flags),
> +		};
> +
> +		ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
> +		if (ret)
> +			break;
> +
> +		node = interval_tree_iter_next(node, 0, -1UL);
> +	}
> +	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
> +
> +	return ret;
> +}
> +
> +/* IOMMU API */
> +
> +static struct iommu_domain *viommu_domain_alloc(unsigned type)
> +{
> +	struct viommu_domain *vdomain;
> +
> +	if (type != IOMMU_DOMAIN_UNMANAGED && type != IOMMU_DOMAIN_DMA)
smmu drivers also support the IDENTITY type. Don't we want to support it
as well?
> +		return NULL;
> +
> +	vdomain = kzalloc(sizeof(*vdomain), GFP_KERNEL);
> +	if (!vdomain)
> +		return NULL;
> +
> +	mutex_init(&vdomain->mutex);
> +	spin_lock_init(&vdomain->mappings_lock);
> +	vdomain->mappings = RB_ROOT_CACHED;
> +
> +	if (type == IOMMU_DOMAIN_DMA &&
> +	    iommu_get_dma_cookie(&vdomain->domain)) {
> +		kfree(vdomain);
> +		return NULL;
> +	}
> +
> +	return &vdomain->domain;
> +}
> +
> +static int viommu_domain_finalise(struct viommu_dev *viommu,
> +				  struct iommu_domain *domain)
> +{
> +	int ret;
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +	unsigned int max_domain = viommu->domain_bits > 31 ? ~0 :
> +				  (1U << viommu->domain_bits) - 1;
> +
> +	vdomain->viommu		= viommu;
> +
> +	domain->pgsize_bitmap	= viommu->pgsize_bitmap;
> +	domain->geometry	= viommu->geometry;
> +
> +	ret = ida_alloc_max(&viommu->domain_ids, max_domain, GFP_KERNEL);
> +	if (ret >= 0)
> +		vdomain->id = (unsigned int)ret;
> +
> +	return ret > 0 ? 0 : ret;
> +}
> +
> +static void viommu_domain_free(struct iommu_domain *domain)
> +{
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	iommu_put_dma_cookie(domain);
> +
> +	/* Free all remaining mappings (size 2^64) */
> +	viommu_del_mappings(vdomain, 0, 0);
> +
> +	if (vdomain->viommu)
> +		ida_free(&vdomain->viommu->domain_ids, vdomain->id);
> +
> +	kfree(vdomain);
> +}
> +
> +static int viommu_attach_dev(struct iommu_domain *domain, struct device
*dev)
> +{
> +	int i;
> +	int ret = 0;
> +	struct virtio_iommu_req_attach req;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +	struct viommu_endpoint *vdev = fwspec->iommu_priv;
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	mutex_lock(&vdomain->mutex);
> +	if (!vdomain->viommu) {
> +		/*
> +		 * Initialize the domain proper now that we know which viommu
properly initialize the domain now we know which viommu owns it?

Thanks

Eric
> +		 * owns it.
> +		 */
> +		ret = viommu_domain_finalise(vdev->viommu, domain);
> +	} else if (vdomain->viommu != vdev->viommu) {
> +		dev_err(dev, "cannot attach to foreign vIOMMU\n");
> +		ret = -EXDEV;
> +	}
> +	mutex_unlock(&vdomain->mutex);
> +
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * In the virtio-iommu device, when attaching the endpoint to a new
> +	 * domain, it is detached from the old one and, if as as a result the
> +	 * old domain isn't attached to any endpoint, all mappings are
removed
> +	 * from the old domain and it is freed.
> +	 *
> +	 * In the driver the old domain still exists, and its mappings will be
> +	 * recreated if it gets reattached to an endpoint. Otherwise it will be
> +	 * freed explicitly.
> +	 *
> +	 * vdev->vdomain is protected by group->mutex
> +	 */
> +	if (vdev->vdomain)
> +		vdev->vdomain->nr_endpoints--;
> +
> +	req = (struct virtio_iommu_req_attach) {
> +		.head.type	= VIRTIO_IOMMU_T_ATTACH,
> +		.domain		= cpu_to_le32(vdomain->id),
> +	};
> +
> +	for (i = 0; i < fwspec->num_ids; i++) {
> +		req.endpoint = cpu_to_le32(fwspec->ids[i]);
> +
> +		ret = viommu_send_req_sync(vdomain->viommu, &req, sizeof(req));
> +		if (ret)
> +			return ret;
> +	}
> +
> +	if (!vdomain->nr_endpoints) {
> +		/*
> +		 * This endpoint is the first to be attached to the domain.
> +		 * Replay existing mappings (e.g. SW MSI).
> +		 */
> +		ret = viommu_replay_mappings(vdomain);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	vdomain->nr_endpoints++;
> +	vdev->vdomain = vdomain;
> +
> +	return 0;
> +}
> +
> +static int viommu_map(struct iommu_domain *domain, unsigned long iova,
> +		      phys_addr_t paddr, size_t size, int prot)
> +{
> +	int ret;
> +	int flags;
> +	struct viommu_mapping *mapping;
> +	struct virtio_iommu_req_map map;
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	flags = (prot & IOMMU_READ ? VIRTIO_IOMMU_MAP_F_READ : 0) |
> +		(prot & IOMMU_WRITE ? VIRTIO_IOMMU_MAP_F_WRITE : 0) |
> +		(prot & IOMMU_MMIO ? VIRTIO_IOMMU_MAP_F_MMIO : 0);
> +
> +	mapping = viommu_add_mapping(vdomain, iova, paddr, size, flags);
> +	if (!mapping)
> +		return -ENOMEM;
> +
> +	map = (struct virtio_iommu_req_map) {
> +		.head.type	= VIRTIO_IOMMU_T_MAP,
> +		.domain		= cpu_to_le32(vdomain->id),
> +		.virt_start	= cpu_to_le64(iova),
> +		.phys_start	= cpu_to_le64(paddr),
> +		.virt_end	= cpu_to_le64(iova + size - 1),
> +		.flags		= cpu_to_le32(flags),
> +	};
> +
> +	if (!vdomain->nr_endpoints)
> +		return 0;
> +
> +	ret = viommu_send_req_sync(vdomain->viommu, &map, sizeof(map));
> +	if (ret)
> +		viommu_del_mappings(vdomain, iova, size);
> +
> +	return ret;
> +}
> +
> +static size_t viommu_unmap(struct iommu_domain *domain, unsigned long
iova,
> +			   size_t size)
> +{
> +	int ret = 0;
> +	size_t unmapped;
> +	struct virtio_iommu_req_unmap unmap;
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	unmapped = viommu_del_mappings(vdomain, iova, size);
> +	if (unmapped < size)
> +		return 0;
> +
> +	/* Device already removed all mappings after detach. */
> +	if (!vdomain->nr_endpoints)
> +		return unmapped;
> +
> +	unmap = (struct virtio_iommu_req_unmap) {
> +		.head.type	= VIRTIO_IOMMU_T_UNMAP,
> +		.domain		= cpu_to_le32(vdomain->id),
> +		.virt_start	= cpu_to_le64(iova),
> +		.virt_end	= cpu_to_le64(iova + unmapped - 1),
> +	};
> +
> +	ret = viommu_add_req(vdomain->viommu, &unmap, sizeof(unmap));
> +	return ret ? 0 : unmapped;
> +}
> +
> +static phys_addr_t viommu_iova_to_phys(struct iommu_domain *domain,
> +				       dma_addr_t iova)
> +{
> +	u64 paddr = 0;
> +	unsigned long flags;
> +	struct viommu_mapping *mapping;
> +	struct interval_tree_node *node;
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	spin_lock_irqsave(&vdomain->mappings_lock, flags);
> +	node = interval_tree_iter_first(&vdomain->mappings, iova, iova);
> +	if (node) {
> +		mapping = container_of(node, struct viommu_mapping, iova);
> +		paddr = mapping->paddr + (iova - mapping->iova.start);
> +	}
> +	spin_unlock_irqrestore(&vdomain->mappings_lock, flags);
> +
> +	return paddr;
> +}
> +
> +static void viommu_iotlb_sync(struct iommu_domain *domain)
> +{
> +	struct viommu_domain *vdomain = to_viommu_domain(domain);
> +
> +	viommu_sync_req(vdomain->viommu);
> +}
> +
> +static void viommu_get_resv_regions(struct device *dev, struct list_head
*head)
> +{
> +	struct iommu_resv_region *region;
> +	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
> +
> +	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
> +					 IOMMU_RESV_SW_MSI);
> +	if (!region)
> +		return;
> +
> +	list_add_tail(&region->list, head);
> +	iommu_dma_get_resv_regions(dev, head);
> +}
> +
> +static void viommu_put_resv_regions(struct device *dev, struct list_head
*head)
> +{
> +	struct iommu_resv_region *entry, *next;
> +
> +	list_for_each_entry_safe(entry, next, head, list)
> +		kfree(entry);
> +}
> +
> +static struct iommu_ops viommu_ops;
> +static struct virtio_driver virtio_iommu_drv;
> +
> +static int viommu_match_node(struct device *dev, void *data)
> +{
> +	return dev->parent->fwnode == data;
> +}
> +
> +static struct viommu_dev *viommu_get_by_fwnode(struct fwnode_handle
*fwnode)
> +{
> +	struct device *dev = driver_find_device(&virtio_iommu_drv.driver,
NULL,
> +						fwnode, viommu_match_node);
> +	put_device(dev);
> +
> +	return dev ? dev_to_virtio(dev)->priv : NULL;
> +}
> +
> +static int viommu_add_device(struct device *dev)
> +{
> +	int ret;
> +	struct iommu_group *group;
> +	struct viommu_endpoint *vdev;
> +	struct viommu_dev *viommu = NULL;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +
> +	if (!fwspec || fwspec->ops != &viommu_ops)
> +		return -ENODEV;
> +
> +	viommu = viommu_get_by_fwnode(fwspec->iommu_fwnode);
> +	if (!viommu)
> +		return -ENODEV;
> +
> +	vdev = kzalloc(sizeof(*vdev), GFP_KERNEL);
> +	if (!vdev)
> +		return -ENOMEM;
> +
> +	vdev->viommu = viommu;
> +	fwspec->iommu_priv = vdev;
> +
> +	ret = iommu_device_link(&viommu->iommu, dev);
> +	if (ret)
> +		goto err_free_dev;
> +
> +	/*
> +	 * Last step creates a default domain and attaches to it. Everything
> +	 * must be ready.
> +	 */
> +	group = iommu_group_get_for_dev(dev);
> +	if (IS_ERR(group)) {
> +		ret = PTR_ERR(group);
> +		goto err_unlink_dev;
> +	}
> +
> +	iommu_group_put(group);
> +
> +	return PTR_ERR_OR_ZERO(group);
> +
> +err_unlink_dev:
> +	iommu_device_unlink(&viommu->iommu, dev);
> +err_free_dev:
> +	kfree(vdev);
> +
> +	return ret;
> +}
> +
> +static void viommu_remove_device(struct device *dev)
> +{
> +	struct viommu_endpoint *vdev;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +
> +	if (!fwspec || fwspec->ops != &viommu_ops)
> +		return;
> +
> +	vdev = fwspec->iommu_priv;
> +
> +	iommu_group_remove_device(dev);
> +	iommu_device_unlink(&vdev->viommu->iommu, dev);
> +	kfree(vdev);
> +}
> +
> +static struct iommu_group *viommu_device_group(struct device *dev)
> +{
> +	if (dev_is_pci(dev))
> +		return pci_device_group(dev);
> +	else
> +		return generic_device_group(dev);
> +}
> +
> +static int viommu_of_xlate(struct device *dev, struct of_phandle_args
*args)
> +{
> +	return iommu_fwspec_add_ids(dev, args->args, 1);
> +}
> +
> +static struct iommu_ops viommu_ops = {
> +	.domain_alloc		= viommu_domain_alloc,
> +	.domain_free		= viommu_domain_free,
> +	.attach_dev		= viommu_attach_dev,
> +	.map			= viommu_map,
> +	.unmap			= viommu_unmap,
> +	.iova_to_phys		= viommu_iova_to_phys,
> +	.iotlb_sync		= viommu_iotlb_sync,
> +	.add_device		= viommu_add_device,
> +	.remove_device		= viommu_remove_device,
> +	.device_group		= viommu_device_group,
> +	.get_resv_regions	= viommu_get_resv_regions,
> +	.put_resv_regions	= viommu_put_resv_regions,
> +	.of_xlate		= viommu_of_xlate,
> +};
> +
> +static int viommu_init_vqs(struct viommu_dev *viommu)
> +{
> +	struct virtio_device *vdev = dev_to_virtio(viommu->dev);
> +	const char *name = "request";
> +	void *ret;
> +
> +	ret = virtio_find_single_vq(vdev, NULL, name);
> +	if (IS_ERR(ret)) {
> +		dev_err(viommu->dev, "cannot find VQ\n");
> +		return PTR_ERR(ret);
> +	}
> +
> +	viommu->vqs[VIOMMU_REQUEST_VQ] = ret;
> +
> +	return 0;
> +}
> +
> +static int viommu_probe(struct virtio_device *vdev)
> +{
> +	struct device *parent_dev = vdev->dev.parent;
> +	struct viommu_dev *viommu = NULL;
> +	struct device *dev = &vdev->dev;
> +	u64 input_start = 0;
> +	u64 input_end = -1UL;
> +	int ret;
> +
> +	if (!virtio_has_feature(vdev, VIRTIO_F_VERSION_1) ||
> +	    !virtio_has_feature(vdev, VIRTIO_IOMMU_F_MAP_UNMAP))
> +		return -ENODEV;
> +
> +	viommu = devm_kzalloc(dev, sizeof(*viommu), GFP_KERNEL);
> +	if (!viommu)
> +		return -ENOMEM;
> +
> +	spin_lock_init(&viommu->request_lock);
> +	ida_init(&viommu->domain_ids);
> +	viommu->dev = dev;
> +	viommu->vdev = vdev;
> +	INIT_LIST_HEAD(&viommu->requests);
> +
> +	ret = viommu_init_vqs(viommu);
> +	if (ret)
> +		return ret;
> +
> +	virtio_cread(vdev, struct virtio_iommu_config, page_size_mask,
> +		     &viommu->pgsize_bitmap);
> +
> +	if (!viommu->pgsize_bitmap) {
> +		ret = -EINVAL;
> +		goto err_free_vqs;
> +	}
> +
> +	viommu->domain_bits = 32;
> +
> +	/* Optional features */
> +	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
> +			     struct virtio_iommu_config, input_range.start,
> +			     &input_start);
> +
> +	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_INPUT_RANGE,
> +			     struct virtio_iommu_config, input_range.end,
> +			     &input_end);
> +
> +	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_DOMAIN_BITS,
> +			     struct virtio_iommu_config, domain_bits,
> +			     &viommu->domain_bits);
> +
> +	viommu->geometry = (struct iommu_domain_geometry) {
> +		.aperture_start	= input_start,
> +		.aperture_end	= input_end,
> +		.force_aperture	= true,
> +	};
> +
> +	viommu_ops.pgsize_bitmap = viommu->pgsize_bitmap;
> +
> +	virtio_device_ready(vdev);
> +
> +	ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL,
"%s",
> +				     virtio_bus_name(vdev));
> +	if (ret)
> +		goto err_free_vqs;
> +
> +	iommu_device_set_ops(&viommu->iommu, &viommu_ops);
> +	iommu_device_set_fwnode(&viommu->iommu, parent_dev->fwnode);
> +
> +	iommu_device_register(&viommu->iommu);
> +
> +#ifdef CONFIG_PCI
> +	if (pci_bus_type.iommu_ops != &viommu_ops) {
> +		pci_request_acs();
> +		ret = bus_set_iommu(&pci_bus_type, &viommu_ops);
> +		if (ret)
> +			goto err_unregister;
> +	}
> +#endif
> +#ifdef CONFIG_ARM_AMBA
> +	if (amba_bustype.iommu_ops != &viommu_ops) {
> +		ret = bus_set_iommu(&amba_bustype, &viommu_ops);
> +		if (ret)
> +			goto err_unregister;
> +	}
> +#endif
> +	if (platform_bus_type.iommu_ops != &viommu_ops) {
> +		ret = bus_set_iommu(&platform_bus_type, &viommu_ops);
> +		if (ret)
> +			goto err_unregister;
> +	}
> +
> +	vdev->priv = viommu;
> +
> +	dev_info(dev, "input address: %u bits\n",
> +		 order_base_2(viommu->geometry.aperture_end));
> +	dev_info(dev, "page mask: %#llx\n", viommu->pgsize_bitmap);
> +
> +	return 0;
> +
> +err_unregister:
> +	iommu_device_sysfs_remove(&viommu->iommu);
> +	iommu_device_unregister(&viommu->iommu);
> +err_free_vqs:
> +	vdev->config->del_vqs(vdev);
> +
> +	return ret;
> +}
> +
> +static void viommu_remove(struct virtio_device *vdev)
> +{
> +	struct viommu_dev *viommu = vdev->priv;
> +
> +	iommu_device_sysfs_remove(&viommu->iommu);
> +	iommu_device_unregister(&viommu->iommu);
> +
> +	/* Stop all virtqueues */
> +	vdev->config->reset(vdev);
> +	vdev->config->del_vqs(vdev);
> +
> +	dev_info(&vdev->dev, "device removed\n");
> +}
> +
> +static void viommu_config_changed(struct virtio_device *vdev)
> +{
> +	dev_warn(&vdev->dev, "config changed\n");
> +}
> +
> +static unsigned int features[] = {
> +	VIRTIO_IOMMU_F_MAP_UNMAP,
> +	VIRTIO_IOMMU_F_DOMAIN_BITS,
> +	VIRTIO_IOMMU_F_INPUT_RANGE,
> +};
> +
> +static struct virtio_device_id id_table[] = {
> +	{ VIRTIO_ID_IOMMU, VIRTIO_DEV_ANY_ID },
> +	{ 0 },
> +};
> +
> +static struct virtio_driver virtio_iommu_drv = {
> +	.driver.name		= KBUILD_MODNAME,
> +	.driver.owner		= THIS_MODULE,
> +	.id_table		= id_table,
> +	.feature_table		= features,
> +	.feature_table_size	= ARRAY_SIZE(features),
> +	.probe			= viommu_probe,
> +	.remove			= viommu_remove,
> +	.config_changed		= viommu_config_changed,
> +};
> +
> +module_virtio_driver(virtio_iommu_drv);
> +
> +MODULE_DESCRIPTION("Virtio IOMMU driver");
> +MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>");
> +MODULE_LICENSE("GPL v2");
> diff --git a/include/uapi/linux/virtio_ids.h
b/include/uapi/linux/virtio_ids.h
> index 6d5c3b2d4f4d..cfe47c5d9a56 100644
> --- a/include/uapi/linux/virtio_ids.h
> +++ b/include/uapi/linux/virtio_ids.h
> @@ -43,5 +43,6 @@
>  #define VIRTIO_ID_INPUT        18 /* virtio input */
>  #define VIRTIO_ID_VSOCK        19 /* virtio vsock transport */
>  #define VIRTIO_ID_CRYPTO       20 /* virtio crypto */
> +#define VIRTIO_ID_IOMMU        23 /* virtio IOMMU */
>  
>  #endif /* _LINUX_VIRTIO_IDS_H */
> diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
> new file mode 100644
> index 000000000000..2e0bf5792f26
> --- /dev/null
> +++ b/include/uapi/linux/virtio_iommu.h
> @@ -0,0 +1,104 @@
> +/* SPDX-License-Identifier: BSD-3-Clause */
> +/*
> + * Virtio-iommu definition v0.8
> + *
> + * Copyright (C) 2018 Arm Ltd.
> + */
> +#ifndef _UAPI_LINUX_VIRTIO_IOMMU_H
> +#define _UAPI_LINUX_VIRTIO_IOMMU_H
> +
> +#include <linux/types.h>
> +
> +/* Feature bits */
> +#define VIRTIO_IOMMU_F_INPUT_RANGE		0
> +#define VIRTIO_IOMMU_F_DOMAIN_BITS		1
> +#define VIRTIO_IOMMU_F_MAP_UNMAP		2
> +#define VIRTIO_IOMMU_F_BYPASS			3
> +
> +struct virtio_iommu_range {
> +	__u64					start;
> +	__u64					end;
> +};
> +
> +struct virtio_iommu_config {
> +	/* Supported page sizes */
> +	__u64					page_size_mask;
> +	/* Supported IOVA range */
> +	struct virtio_iommu_range		input_range;
> +	/* Max domain ID size */
> +	__u8					domain_bits;
> +	__u8					padding[3];
> +};
> +
> +/* Request types */
> +#define VIRTIO_IOMMU_T_ATTACH			0x01
> +#define VIRTIO_IOMMU_T_DETACH			0x02
> +#define VIRTIO_IOMMU_T_MAP			0x03
> +#define VIRTIO_IOMMU_T_UNMAP			0x04
> +
> +/* Status types */
> +#define VIRTIO_IOMMU_S_OK			0x00
> +#define VIRTIO_IOMMU_S_IOERR			0x01
> +#define VIRTIO_IOMMU_S_UNSUPP			0x02
> +#define VIRTIO_IOMMU_S_DEVERR			0x03
> +#define VIRTIO_IOMMU_S_INVAL			0x04
> +#define VIRTIO_IOMMU_S_RANGE			0x05
> +#define VIRTIO_IOMMU_S_NOENT			0x06
> +#define VIRTIO_IOMMU_S_FAULT			0x07
> +
> +struct virtio_iommu_req_head {
> +	__u8					type;
> +	__u8					reserved[3];
> +};
> +
> +struct virtio_iommu_req_tail {
> +	__u8					status;
> +	__u8					reserved[3];
> +};
> +
> +struct virtio_iommu_req_attach {
> +	struct virtio_iommu_req_head		head;
> +	__le32					domain;
> +	__le32					endpoint;
> +	__u8					reserved[8];
> +	struct virtio_iommu_req_tail		tail;
> +};
> +
> +struct virtio_iommu_req_detach {
> +	struct virtio_iommu_req_head		head;
> +	__le32					domain;
> +	__le32					endpoint;
> +	__u8					reserved[8];
> +	struct virtio_iommu_req_tail		tail;
> +};
> +
> +#define VIRTIO_IOMMU_MAP_F_READ			(1 << 0)
> +#define VIRTIO_IOMMU_MAP_F_WRITE		(1 << 1)
> +#define VIRTIO_IOMMU_MAP_F_EXEC			(1 << 2)
> +#define VIRTIO_IOMMU_MAP_F_MMIO			(1 << 3)
> +
> +#define VIRTIO_IOMMU_MAP_F_MASK			(VIRTIO_IOMMU_MAP_F_READ |	\
> +						 VIRTIO_IOMMU_MAP_F_WRITE |	\
> +						 VIRTIO_IOMMU_MAP_F_EXEC |	\
> +						 VIRTIO_IOMMU_MAP_F_MMIO)
> +
> +struct virtio_iommu_req_map {
> +	struct virtio_iommu_req_head		head;
> +	__le32					domain;
> +	__le64					virt_start;
> +	__le64					virt_end;
> +	__le64					phys_start;
> +	__le32					flags;
> +	struct virtio_iommu_req_tail		tail;
> +};
> +
> +struct virtio_iommu_req_unmap {
> +	struct virtio_iommu_req_head		head;
> +	__le32					domain;
> +	__le64					virt_start;
> +	__le64					virt_end;
> +	__u8					reserved[4];
> +	struct virtio_iommu_req_tail		tail;
> +};
> +
> +#endif
>

Hi Jean,

On 11/15/18 5:52 PM, Jean-Philippe Brucker wrote:
> The event queue offers a way for the device to report access faults from
> endpoints. It is implemented on virtqueue #1. Whenever the host needs to
> signal a fault, it fills one of the buffers offered by the guest and
> interrupts it.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>
> ---
>  drivers/iommu/virtio-iommu.c      | 116 +++++++++++++++++++++++++++---
>  include/uapi/linux/virtio_iommu.h |  19 +++++
>  2 files changed, 126 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index c547ebd79c43..81c6b72e9c43 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -29,7 +29,8 @@
>  #define MSI_IOVA_LENGTH			0x100000
>  
>  #define VIOMMU_REQUEST_VQ		0
> -#define VIOMMU_NR_VQS			1
> +#define VIOMMU_EVENT_VQ			1
> +#define VIOMMU_NR_VQS			2
>  
>  struct viommu_dev {
>  	struct iommu_device		iommu;
> @@ -41,6 +42,7 @@ struct viommu_dev {
>  	struct virtqueue		*vqs[VIOMMU_NR_VQS];
>  	spinlock_t			request_lock;
>  	struct list_head		requests;
> +	void				*evts;
>  
>  	/* Device configuration */
>  	struct iommu_domain_geometry	geometry;
> @@ -82,6 +84,15 @@ struct viommu_request {
>  	char				buf[];
>  };
>  
> +#define VIOMMU_FAULT_RESV_MASK		0xffffff00
> +
> +struct viommu_event {
> +	union {
> +		u32			head;
> +		struct virtio_iommu_fault fault;
> +	};
> +};
> +
>  #define to_viommu_domain(domain)	\
>  	container_of(domain, struct viommu_domain, domain)
>  
> @@ -504,6 +515,69 @@ static int viommu_probe_endpoint(struct viommu_dev
*viommu, struct device *dev)
>  	return ret;
>  }
>  
> +static int viommu_fault_handler(struct viommu_dev *viommu,
> +				struct virtio_iommu_fault *fault)
> +{
> +	char *reason_str;
> +
> +	u8 reason	= fault->reason;
> +	u32 flags	= le32_to_cpu(fault->flags);
> +	u32 endpoint	= le32_to_cpu(fault->endpoint);
> +	u64 address	= le64_to_cpu(fault->address);
> +
> +	switch (reason) {
> +	case VIRTIO_IOMMU_FAULT_R_DOMAIN:
> +		reason_str = "domain";
> +		break;
> +	case VIRTIO_IOMMU_FAULT_R_MAPPING:
> +		reason_str = "page";
> +		break;
> +	case VIRTIO_IOMMU_FAULT_R_UNKNOWN:
> +	default:
> +		reason_str = "unknown";
> +		break;
> +	}
> +
> +	/* TODO: find EP by ID and report_iommu_fault */
> +	if (flags & VIRTIO_IOMMU_FAULT_F_ADDRESS)
> +		dev_err_ratelimited(viommu->dev, "%s fault from EP %u at %#llx
[%s%s%s]\n",
> +				    reason_str, endpoint, address,
> +				    flags & VIRTIO_IOMMU_FAULT_F_READ ? "R" :
"",
> +				    flags & VIRTIO_IOMMU_FAULT_F_WRITE ? "W" :
"",
> +				    flags & VIRTIO_IOMMU_FAULT_F_EXEC ? "X" :
"");
> +	else
> +		dev_err_ratelimited(viommu->dev, "%s fault from EP %u\n",
> +				    reason_str, endpoint);
> +	return 0;
> +}
> +
> +static void viommu_event_handler(struct virtqueue *vq)
> +{
> +	int ret;
> +	unsigned int len;
> +	struct scatterlist sg[1];
> +	struct viommu_event *evt;
> +	struct viommu_dev *viommu = vq->vdev->priv;
> +
> +	while ((evt = virtqueue_get_buf(vq, &len)) != NULL) {
> +		if (len > sizeof(*evt)) {
> +			dev_err(viommu->dev,
> +				"invalid event buffer (len %u != %zu)\n",
> +				len, sizeof(*evt));
> +		} else if (!(evt->head & VIOMMU_FAULT_RESV_MASK)) {
> +			viommu_fault_handler(viommu, &evt->fault);
> +		}
> +
> +		sg_init_one(sg, evt, sizeof(*evt));
> +		ret = virtqueue_add_inbuf(vq, sg, 1, evt, GFP_ATOMIC);
> +		if (ret)
> +			dev_err(viommu->dev, "could not add event buffer\n");
> +	}
> +
> +	if (!virtqueue_kick(vq))
> +		dev_err(viommu->dev, "kick failed\n");
There are other occurences of virtqueue_kick where you don't check the
returned value
> +}
> +
>  /* IOMMU API */
>  
>  static struct iommu_domain *viommu_domain_alloc(unsigned type)
> @@ -887,16 +961,35 @@ static struct iommu_ops viommu_ops = {
>  static int viommu_init_vqs(struct viommu_dev *viommu)
>  {
>  	struct virtio_device *vdev = dev_to_virtio(viommu->dev);
> -	const char *name = "request";
> -	void *ret;
> +	const char *names[] = { "request", "event" };
> +	vq_callback_t *callbacks[] = {
> +		NULL, /* No async requests */
> +		viommu_event_handler,
> +	};
>  
> -	ret = virtio_find_single_vq(vdev, NULL, name);
> -	if (IS_ERR(ret)) {
> -		dev_err(viommu->dev, "cannot find VQ\n");
> -		return PTR_ERR(ret);
> -	}
> +	return virtio_find_vqs(vdev, VIOMMU_NR_VQS, viommu->vqs, callbacks,
> +			       names, NULL);
> +}
>  
> -	viommu->vqs[VIOMMU_REQUEST_VQ] = ret;
> +static int viommu_fill_evtq(struct viommu_dev *viommu)
> +{
> +	int i, ret;
> +	struct scatterlist sg[1];
> +	struct viommu_event *evts;
> +	struct virtqueue *vq = viommu->vqs[VIOMMU_EVENT_VQ];
> +	size_t nr_evts = vq->num_free;
> +
> +	viommu->evts = evts = devm_kmalloc_array(viommu->dev, nr_evts,
> +						 sizeof(*evts), GFP_KERNEL);
> +	if (!evts)
> +		return -ENOMEM;
> +
> +	for (i = 0; i < nr_evts; i++) {
> +		sg_init_one(sg, &evts[i], sizeof(*evts));
> +		ret = virtqueue_add_inbuf(vq, sg, 1, &evts[i], GFP_KERNEL);
> +		if (ret)
> +			return ret;
> +	}
>  
>  	return 0;
>  }
> @@ -965,6 +1058,11 @@ static int viommu_probe(struct virtio_device *vdev)
>  
>  	virtio_device_ready(vdev);
>  
> +	/* Populate the event queue with buffers */
> +	ret = viommu_fill_evtq(viommu);
> +	if (ret)
> +		goto err_free_vqs;
> +
>  	ret = iommu_device_sysfs_add(&viommu->iommu, dev, NULL,
"%s",
>  				     virtio_bus_name(vdev));
>  	if (ret)
> diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
> index cde2a3409caa..fed2ba5b47ab 100644
> --- a/include/uapi/linux/virtio_iommu.h
> +++ b/include/uapi/linux/virtio_iommu.h
> @@ -139,4 +139,23 @@ struct virtio_iommu_req_probe {
>  	 */
>  };
>  
> +/* Fault types */
> +#define VIRTIO_IOMMU_FAULT_R_UNKNOWN		0
> +#define VIRTIO_IOMMU_FAULT_R_DOMAIN		1
> +#define VIRTIO_IOMMU_FAULT_R_MAPPING		2
> +
> +#define VIRTIO_IOMMU_FAULT_F_READ		(1 << 0)
> +#define VIRTIO_IOMMU_FAULT_F_WRITE		(1 << 1)
> +#define VIRTIO_IOMMU_FAULT_F_EXEC		(1 << 2)
> +#define VIRTIO_IOMMU_FAULT_F_ADDRESS		(1 << 8)
> +
> +struct virtio_iommu_fault {
> +	__u8					reason;
> +	__u8					reserved[3];
> +	__le32					flags;
> +	__le32					endpoint;
> +	__u8					reserved2[4];
> +	__le64					address;
> +};
> +
>  #endif
> 
Reviewed-by: Eric Auger <eric.auger at redhat.com>

Thanks

Eric

Hi Jean,

On 11/15/18 5:52 PM, Jean-Philippe Brucker wrote:
> When the device offers the probe feature, send a probe request for each
> device managed by the IOMMU. Extract RESV_MEM information. When we
> encounter a MSI doorbell region, set it up as a IOMMU_RESV_MSI region.
> This will tell other subsystems that there is no need to map the MSI
> doorbell in the virtio-iommu, because MSIs bypass it.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>
Reviewed-by: Eric Auger <eric.auger at redhat.com>

Thanks

Eric
> ---
>  drivers/iommu/virtio-iommu.c      | 156 ++++++++++++++++++++++++++++--
>  include/uapi/linux/virtio_iommu.h |  38 ++++++++
>  2 files changed, 188 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
> index 2a9cb6285a1e..c547ebd79c43 100644
> --- a/drivers/iommu/virtio-iommu.c
> +++ b/drivers/iommu/virtio-iommu.c
> @@ -46,6 +46,7 @@ struct viommu_dev {
>  	struct iommu_domain_geometry	geometry;
>  	u64				pgsize_bitmap;
>  	u8				domain_bits;
> +	u32				probe_size;
>  };
>  
>  struct viommu_mapping {
> @@ -67,8 +68,10 @@ struct viommu_domain {
>  };
>  
>  struct viommu_endpoint {
> +	struct device			*dev;
>  	struct viommu_dev		*viommu;
>  	struct viommu_domain		*vdomain;
> +	struct list_head		resv_regions;
>  };
>  
>  struct viommu_request {
> @@ -119,6 +122,9 @@ static off_t viommu_get_req_offset(struct viommu_dev
*viommu,
>  {
>  	size_t tail_size = sizeof(struct virtio_iommu_req_tail);
>  
> +	if (req->type == VIRTIO_IOMMU_T_PROBE)
> +		return len - viommu->probe_size - tail_size;
> +
>  	return len - tail_size;
>  }
>  
> @@ -394,6 +400,110 @@ static int viommu_replay_mappings(struct
viommu_domain *vdomain)
>  	return ret;
>  }
>  
> +static int viommu_add_resv_mem(struct viommu_endpoint *vdev,
> +			       struct virtio_iommu_probe_resv_mem *mem,
> +			       size_t len)
> +{
> +	size_t size;
> +	u64 start64, end64;
> +	phys_addr_t start, end;
> +	struct iommu_resv_region *region = NULL;
> +	unsigned long prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
> +
> +	start = start64 = le64_to_cpu(mem->start);
> +	end = end64 = le64_to_cpu(mem->end);
> +	size = end64 - start64 + 1;
> +
> +	/* Catch any overflow, including the unlikely end64 - start64 + 1 = 0 */
> +	if (start != start64 || end != end64 || size < end64 - start64)
> +		return -EOVERFLOW;
> +
> +	if (len < sizeof(*mem))
> +		return -EINVAL;
> +
> +	switch (mem->subtype) {
> +	default:
> +		dev_warn(vdev->dev, "unknown resv mem subtype 0x%x\n",
> +			 mem->subtype);
> +		/* Fall-through */
> +	case VIRTIO_IOMMU_RESV_MEM_T_RESERVED:
> +		region = iommu_alloc_resv_region(start, size, 0,
> +						 IOMMU_RESV_RESERVED);
> +		break;
> +	case VIRTIO_IOMMU_RESV_MEM_T_MSI:
> +		region = iommu_alloc_resv_region(start, size, prot,
> +						 IOMMU_RESV_MSI);
> +		break;
> +	}
> +	if (!region)
> +		return -ENOMEM;
> +
> +	list_add(&vdev->resv_regions, &region->list);
> +	return 0;
> +}
> +
> +static int viommu_probe_endpoint(struct viommu_dev *viommu, struct device
*dev)
> +{
> +	int ret;
> +	u16 type, len;
> +	size_t cur = 0;
> +	size_t probe_len;
> +	struct virtio_iommu_req_probe *probe;
> +	struct virtio_iommu_probe_property *prop;
> +	struct iommu_fwspec *fwspec = dev->iommu_fwspec;
> +	struct viommu_endpoint *vdev = fwspec->iommu_priv;
> +
> +	if (!fwspec->num_ids)
> +		return -EINVAL;
> +
> +	probe_len = sizeof(*probe) + viommu->probe_size +
> +		    sizeof(struct virtio_iommu_req_tail);
> +	probe = kzalloc(probe_len, GFP_KERNEL);
> +	if (!probe)
> +		return -ENOMEM;
> +
> +	probe->head.type = VIRTIO_IOMMU_T_PROBE;
> +	/*
> +	 * For now, assume that properties of an endpoint that outputs multiple
> +	 * IDs are consistent. Only probe the first one.
> +	 */
> +	probe->endpoint = cpu_to_le32(fwspec->ids[0]);
> +
> +	ret = viommu_send_req_sync(viommu, probe, probe_len);
> +	if (ret)
> +		goto out_free;
> +
> +	prop = (void *)probe->properties;
> +	type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
> +
> +	while (type != VIRTIO_IOMMU_PROBE_T_NONE &&
> +	       cur < viommu->probe_size) {
> +		len = le16_to_cpu(prop->length) + sizeof(*prop);
> +
> +		switch (type) {
> +		case VIRTIO_IOMMU_PROBE_T_RESV_MEM:
> +			ret = viommu_add_resv_mem(vdev, (void *)prop, len);
> +			break;
> +		default:
> +			dev_err(dev, "unknown viommu prop 0x%x\n", type);
> +		}
> +
> +		if (ret)
> +			dev_err(dev, "failed to parse viommu prop 0x%x\n", type);
> +
> +		cur += len;
> +		if (cur >= viommu->probe_size)
> +			break;
> +
> +		prop = (void *)probe->properties + cur;
> +		type = le16_to_cpu(prop->type) & VIRTIO_IOMMU_PROBE_T_MASK;
> +	}
> +
> +out_free:
> +	kfree(probe);
> +	return ret;
> +}
> +
>  /* IOMMU API */
>  
>  static struct iommu_domain *viommu_domain_alloc(unsigned type)
> @@ -616,15 +726,33 @@ static void viommu_iotlb_sync(struct iommu_domain
*domain)
>  
>  static void viommu_get_resv_regions(struct device *dev, struct list_head
*head)
>  {
> -	struct iommu_resv_region *region;
> +	struct iommu_resv_region *entry, *new_entry, *msi = NULL;
> +	struct viommu_endpoint *vdev = dev->iommu_fwspec->iommu_priv;
>  	int prot = IOMMU_WRITE | IOMMU_NOEXEC | IOMMU_MMIO;
>  
> -	region = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH, prot,
> -					 IOMMU_RESV_SW_MSI);
> -	if (!region)
> -		return;
> +	list_for_each_entry(entry, &vdev->resv_regions, list) {
> +		if (entry->type == IOMMU_RESV_MSI)
> +			msi = entry;
> +
> +		new_entry = kmemdup(entry, sizeof(*entry), GFP_KERNEL);
> +		if (!new_entry)
> +			return;
> +		list_add_tail(&new_entry->list, head);
> +	}
> +
> +	/*
> +	 * If the device didn't register any bypass MSI window, add a
> +	 * software-mapped region.
> +	 */
> +	if (!msi) {
> +		msi = iommu_alloc_resv_region(MSI_IOVA_BASE, MSI_IOVA_LENGTH,
> +					      prot, IOMMU_RESV_SW_MSI);
> +		if (!msi)
> +			return;
> +
> +		list_add_tail(&msi->list, head);
> +	}
>  
> -	list_add_tail(&region->list, head);
>  	iommu_dma_get_resv_regions(dev, head);
>  }
>  
> @@ -672,9 +800,18 @@ static int viommu_add_device(struct device *dev)
>  	if (!vdev)
>  		return -ENOMEM;
>  
> +	vdev->dev = dev;
>  	vdev->viommu = viommu;
> +	INIT_LIST_HEAD(&vdev->resv_regions);
>  	fwspec->iommu_priv = vdev;
>  
> +	if (viommu->probe_size) {
> +		/* Get additional information for this endpoint */
> +		ret = viommu_probe_endpoint(viommu, dev);
> +		if (ret)
> +			goto err_free_dev;
> +	}
> +
>  	ret = iommu_device_link(&viommu->iommu, dev);
>  	if (ret)
>  		goto err_free_dev;
> @@ -696,6 +833,7 @@ static int viommu_add_device(struct device *dev)
>  err_unlink_dev:
>  	iommu_device_unlink(&viommu->iommu, dev);
>  err_free_dev:
> +	viommu_put_resv_regions(dev, &vdev->resv_regions);
>  	kfree(vdev);
>  
>  	return ret;
> @@ -713,6 +851,7 @@ static void viommu_remove_device(struct device *dev)
>  
>  	iommu_group_remove_device(dev);
>  	iommu_device_unlink(&vdev->viommu->iommu, dev);
> +	viommu_put_resv_regions(dev, &vdev->resv_regions);
>  	kfree(vdev);
>  }
>  
> @@ -812,6 +951,10 @@ static int viommu_probe(struct virtio_device *vdev)
>  			     struct virtio_iommu_config, domain_bits,
>  			     &viommu->domain_bits);
>  
> +	virtio_cread_feature(vdev, VIRTIO_IOMMU_F_PROBE,
> +			     struct virtio_iommu_config, probe_size,
> +			     &viommu->probe_size);
> +
>  	viommu->geometry = (struct iommu_domain_geometry) {
>  		.aperture_start	= input_start,
>  		.aperture_end	= input_end,
> @@ -893,6 +1036,7 @@ static unsigned int features[] = {
>  	VIRTIO_IOMMU_F_MAP_UNMAP,
>  	VIRTIO_IOMMU_F_DOMAIN_BITS,
>  	VIRTIO_IOMMU_F_INPUT_RANGE,
> +	VIRTIO_IOMMU_F_PROBE,
>  };
>  
>  static struct virtio_device_id id_table[] = {
> diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
> index 2e0bf5792f26..cde2a3409caa 100644
> --- a/include/uapi/linux/virtio_iommu.h
> +++ b/include/uapi/linux/virtio_iommu.h
> @@ -14,6 +14,7 @@
>  #define VIRTIO_IOMMU_F_DOMAIN_BITS		1
>  #define VIRTIO_IOMMU_F_MAP_UNMAP		2
>  #define VIRTIO_IOMMU_F_BYPASS			3
> +#define VIRTIO_IOMMU_F_PROBE			4
>  
>  struct virtio_iommu_range {
>  	__u64					start;
> @@ -28,6 +29,8 @@ struct virtio_iommu_config {
>  	/* Max domain ID size */
>  	__u8					domain_bits;
>  	__u8					padding[3];
> +	/* Probe buffer size */
> +	__u32					probe_size;
>  };
>  
>  /* Request types */
> @@ -35,6 +38,7 @@ struct virtio_iommu_config {
>  #define VIRTIO_IOMMU_T_DETACH			0x02
>  #define VIRTIO_IOMMU_T_MAP			0x03
>  #define VIRTIO_IOMMU_T_UNMAP			0x04
> +#define VIRTIO_IOMMU_T_PROBE			0x05
>  
>  /* Status types */
>  #define VIRTIO_IOMMU_S_OK			0x00
> @@ -101,4 +105,38 @@ struct virtio_iommu_req_unmap {
>  	struct virtio_iommu_req_tail		tail;
>  };
>  
> +#define VIRTIO_IOMMU_PROBE_T_NONE		0
> +#define VIRTIO_IOMMU_PROBE_T_RESV_MEM		1
> +
> +#define VIRTIO_IOMMU_PROBE_T_MASK		0xfff
> +
> +struct virtio_iommu_probe_property {
> +	__le16					type;
> +	__le16					length;
> +};
> +
> +#define VIRTIO_IOMMU_RESV_MEM_T_RESERVED	0
> +#define VIRTIO_IOMMU_RESV_MEM_T_MSI		1
> +
> +struct virtio_iommu_probe_resv_mem {
> +	struct virtio_iommu_probe_property	head;
> +	__u8					subtype;
> +	__u8					reserved[3];
> +	__le64					start;
> +	__le64					end;
> +};
> +
> +struct virtio_iommu_req_probe {
> +	struct virtio_iommu_req_head		head;
> +	__le32					endpoint;
> +	__u8					reserved[64];
> +
> +	__u8					properties[];
> +
> +	/*
> +	 * Tail follows the variable-length properties array. No padding,
> +	 * property lengths are all aligned on 8 bytes.
> +	 */
> +};
> +
>  #endif
>

Hi Jean,
On 11/15/18 5:52 PM, Jean-Philippe Brucker wrote:
> Implement the virtio-iommu driver, following specification v0.8 [1].
> 
> Changes since v3 [2]:
> * Rebase onto v4.20-rc2. Patch 3 now touches drivers/of/base.c instead
>   of drivers/pci/of.c, since the map_rid() function has moved.
> * Removed the request timeout, that depended on DEBUG.
> * Other small fixes addressing comments on v3.
> 
> You can find Linux driver and kvmtool device on my virtio-iommu/v0.8.1
> branches [3]. You can also test it with the latest version of Eric's
> QEMU device [4].
Tested-by: Eric Auger <eric.auger at redhat.com>

this was tested with qemu
(https://github.com/eauger/qemu/tree/v3.1.0-rc1-virtio-iommu-v0.8.1)

Thanks

Eric
> 
> [1] Virtio-iommu specification v0.8, sources and pdf
>     git://linux-arm.org/virtio-iommu.git virtio-iommu/v0.8
>     http://jpbrucker.net/virtio-iommu/spec/v0.8/virtio-iommu-v0.8.pdf
> 
> [2] [PATCH v3 0/7] Add virtio-iommu driver
>     https://www.spinics.net/lists/linux-pci/msg77110.html
> 
> [3] git://linux-arm.org/linux-jpb.git virtio-iommu/v0.8.1
>     git://linux-arm.org/kvmtool-jpb.git virtio-iommu/v0.8.1
> 
> [4] [RFC v8 00/18] VIRTIO-IOMMU device
>     https://www.mail-archive.com/qemu-devel at nongnu.org/msg572637.html
> 
> Jean-Philippe Brucker (7):
>   dt-bindings: virtio-mmio: Add IOMMU description
>   dt-bindings: virtio: Add virtio-pci-iommu node
>   of: Allow the iommu-map property to omit untranslated devices
>   PCI: OF: Initialize dev->fwnode appropriately
>   iommu: Add virtio-iommu driver
>   iommu/virtio: Add probe request
>   iommu/virtio: Add event queue
> 
>  .../devicetree/bindings/virtio/iommu.txt      |   66 +
>  .../devicetree/bindings/virtio/mmio.txt       |   30 +
>  MAINTAINERS                                   |    7 +
>  drivers/iommu/Kconfig                         |   11 +
>  drivers/iommu/Makefile                        |    1 +
>  drivers/iommu/virtio-iommu.c                  | 1160 +++++++++++++++++
>  drivers/of/base.c                             |   10 +-
>  drivers/pci/of.c                              |    7 +
>  include/uapi/linux/virtio_ids.h               |    1 +
>  include/uapi/linux/virtio_iommu.h             |  161 +++
>  10 files changed, 1451 insertions(+), 3 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt
>  create mode 100644 drivers/iommu/virtio-iommu.c
>  create mode 100644 include/uapi/linux/virtio_iommu.h
>

On Thu, 15 Nov 2018 16:52:30 +0000, Jean-Philippe Brucker
wrote:
> In PCI root complex nodes, the iommu-map property describes the IOMMU that
> translates each endpoint. On some platforms, the IOMMU itself is presented
> as a PCI endpoint (e.g. AMD IOMMU and virtio-iommu). This isn't
supported
> by the current OF driver, which expects all endpoints to have an IOMMU.
> Allow the iommu-map property to have gaps.
> 
> Relaxing of_map_rid() also allows the msi-map property to have gaps, which
> is invalid since MSIs always reach an MSI controller. In that case
> pci_msi_setup_msi_irqs() will return an error when attempting to find the
> device's MSI domain.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker at
arm.com>
> ---
>  drivers/of/base.c | 10 +++++++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
> 
Reviewed-by: Rob Herring <robh at kernel.org>