Jean-Philippe Brucker
2020-Feb-14 16:04 UTC
[PATCH 0/3] virtio-iommu on non-devicetree platforms
Add topology description to the virtio-iommu driver and enable x86
platforms. Since the RFC [1] I've mostly given up on ACPI tables, since
the internal discussions seem to have reached a dead end. The built-in
topology description presented here isn't ideal, but it is simple to
implement and doesn't impose a dependency on ACPI or device-tree, which
can be beneficial to lightweight hypervisors.
The built-in description is an array in the virtio config space. The
driver parses the config space early and postpones endpoint probe until
the virtio-iommu device is ready. Each element in the array describes
either a PCI range or a single MMIO endpoint, and their associated
endpoint IDs:
struct virtio_iommu_topo_pci_range {
__le16 type; /* 1: PCI range */
__le16 hierarchy; /* PCI domain number */
__le16 requester_start; /* First BDF */
__le16 requester_end; /* Last BDF */
__le32 endpoint_start; /* First endpoint ID */
};
struct virtio_iommu_topo_endpoint {
__le16 type; /* 2: Endpoint */
__le16 reserved; /* 0 */
__le32 endpoint; /* Endpoint ID */
__le64 address; /* First MMIO address */
};
You can find the QEMU patches based on Eric's latest device on my
virtio-iommu/devel branch [2]. I test on both x86 q35, and aarch64 virt
machine with edk2.
[1] https://lore.kernel.org/linux-iommu/20191122105000.800410-1-jean-philippe at
linaro.org/
[2] https://jpbrucker.net/git/qemu virtio-iommu/devel
Jean-Philippe Brucker (3):
iommu/virtio: Add topology description to virtio-iommu config space
PCI: Add DMA configuration for virtual platforms
iommu/virtio: Enable x86 support
MAINTAINERS | 2 +
drivers/iommu/Kconfig | 13 +-
drivers/iommu/Makefile | 1 +
drivers/iommu/virtio-iommu-topology.c | 343 ++++++++++++++++++++++++++
drivers/iommu/virtio-iommu.c | 3 +
drivers/pci/pci-driver.c | 5 +
include/linux/virt_iommu.h | 19 ++
include/uapi/linux/virtio_iommu.h | 26 ++
8 files changed, 411 insertions(+), 1 deletion(-)
create mode 100644 drivers/iommu/virtio-iommu-topology.c
create mode 100644 include/linux/virt_iommu.h
--
2.25.0
Jean-Philippe Brucker
2020-Feb-14 16:04 UTC
[PATCH 1/3] iommu/virtio: Add topology description to virtio-iommu config space
Platforms without device-tree do not currently have a method for
describing the vIOMMU topology. Provide a topology description embedded
into the virtio device.
Use PCI FIXUP to probe the config space early, because we need to
discover the topology before any DMA configuration takes place, and the
virtio driver may be loaded much later. Since we discover the topology
description when probing the PCI hierarchy, the virtual IOMMU cannot
manage other platform devices discovered earlier.
This solution isn't elegant nor foolproof, but is the best we can do at
the moment and works with existing virtio-iommu implementations. It also
enables an IOMMU for lightweight hypervisors that do not rely on
firmware methods for booting.
Signed-off-by: Eric Auger <eric.auger at redhat.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org>
---
MAINTAINERS | 2 +
drivers/iommu/Kconfig | 10 +
drivers/iommu/Makefile | 1 +
drivers/iommu/virtio-iommu-topology.c | 343 ++++++++++++++++++++++++++
drivers/iommu/virtio-iommu.c | 3 +
include/linux/virt_iommu.h | 19 ++
include/uapi/linux/virtio_iommu.h | 26 ++
7 files changed, 404 insertions(+)
create mode 100644 drivers/iommu/virtio-iommu-topology.c
create mode 100644 include/linux/virt_iommu.h
diff --git a/MAINTAINERS b/MAINTAINERS
index 38fe2f3f7b6f..6b978b0d0c90 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -17780,6 +17780,8 @@ M: Jean-Philippe Brucker <jean-philippe at
linaro.org>
L: virtualization at lists.linux-foundation.org
S: Maintained
F: drivers/iommu/virtio-iommu.c
+F: drivers/iommu/virtio-iommu-topology.c
+F: include/linux/virt_iommu.h
F: include/uapi/linux/virtio_iommu.h
VIRTUAL BOX GUEST DEVICE DRIVER
diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index d2fade984999..068d4e0e3541 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -516,4 +516,14 @@ config VIRTIO_IOMMU
Say Y here if you intend to run this kernel as a guest.
+config VIRTIO_IOMMU_TOPOLOGY
+ bool "Topology properties for the virtio-iommu"
+ depends on VIRTIO_IOMMU
+ default y
+ help
+ Enable early probing of the virtio-iommu device, to detect the
+ built-in topology description.
+
+ 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 2104fb8afc06..f295cacf9c6e 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -37,3 +37,4 @@ obj-$(CONFIG_S390_IOMMU) += s390-iommu.o
obj-$(CONFIG_QCOM_IOMMU) += qcom_iommu.o
obj-$(CONFIG_HYPERV_IOMMU) += hyperv-iommu.o
obj-$(CONFIG_VIRTIO_IOMMU) += virtio-iommu.o
+obj-$(CONFIG_VIRTIO_IOMMU_TOPOLOGY) += virtio-iommu-topology.o
diff --git a/drivers/iommu/virtio-iommu-topology.c
b/drivers/iommu/virtio-iommu-topology.c
new file mode 100644
index 000000000000..e4ab49701df5
--- /dev/null
+++ b/drivers/iommu/virtio-iommu-topology.c
@@ -0,0 +1,343 @@
+// SPDX-License-Identifier: GPL-2.0
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/dma-iommu.h>
+#include <linux/list.h>
+#include <linux/pci.h>
+#include <linux/virt_iommu.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_pci.h>
+#include <uapi/linux/virtio_iommu.h>
+
+struct viommu_cap_config {
+ u8 bar;
+ u32 length; /* structure size */
+ u32 offset; /* structure offset within the bar */
+};
+
+union viommu_topo_cfg {
+ __le16 type;
+ struct virtio_iommu_topo_pci_range pci;
+ struct virtio_iommu_topo_endpoint ep;
+};
+
+struct viommu_spec {
+ struct device *dev; /* transport device */
+ struct fwnode_handle *fwnode;
+ struct iommu_ops *ops;
+ struct list_head list;
+ size_t num_items;
+ /* The config array of length num_items follows */
+ union viommu_topo_cfg cfg[];
+};
+
+static LIST_HEAD(viommus);
+static DEFINE_MUTEX(viommus_lock);
+
+#define VPCI_FIELD(field) offsetof(struct virtio_pci_cap, field)
+
+static inline int viommu_pci_find_capability(struct pci_dev *dev, u8 cfg_type,
+ struct viommu_cap_config *cap)
+{
+ int pos;
+ u8 bar;
+
+ for (pos = pci_find_capability(dev, PCI_CAP_ID_VNDR);
+ pos > 0;
+ pos = pci_find_next_capability(dev, pos, PCI_CAP_ID_VNDR)) {
+ u8 type;
+
+ pci_read_config_byte(dev, pos + VPCI_FIELD(cfg_type), &type);
+ if (type != cfg_type)
+ continue;
+
+ pci_read_config_byte(dev, pos + VPCI_FIELD(bar), &bar);
+
+ /* Ignore structures with reserved BAR values */
+ if (type != VIRTIO_PCI_CAP_PCI_CFG && bar > 0x5)
+ continue;
+
+ cap->bar = bar;
+ pci_read_config_dword(dev, pos + VPCI_FIELD(length),
+ &cap->length);
+ pci_read_config_dword(dev, pos + VPCI_FIELD(offset),
+ &cap->offset);
+
+ return pos;
+ }
+ return 0;
+}
+
+static void viommu_ccopy(__le32 *dst, u32 __iomem *src, size_t length)
+{
+ size_t i;
+
+ /* For the moment all our config structures align on 32b */
+ if (WARN_ON(length % 4))
+ return;
+
+ for (i = 0; i < length / 4; i++)
+ /* Keep little-endian data */
+ dst[i] = cpu_to_le32(ioread32(src + i));
+}
+
+static int viommu_parse_topology(struct device *dev,
+ struct virtio_iommu_config __iomem *cfg)
+{
+ size_t i;
+ size_t spec_length;
+ struct viommu_spec *viommu_spec;
+ u32 offset, item_length, num_items;
+
+ offset = ioread32(&cfg->topo_config.offset);
+ item_length = ioread32(&cfg->topo_config.item_length);
+ num_items = ioread32(&cfg->topo_config.num_items);
+ if (!offset || !num_items || !item_length)
+ return 0;
+
+ spec_length = sizeof(*viommu_spec) + num_items *
+ sizeof(union viommu_topo_cfg);
+ viommu_spec = kzalloc(spec_length, GFP_KERNEL);
+ if (!viommu_spec)
+ return -ENOMEM;
+
+ viommu_spec->dev = dev;
+
+ /* Copy in the whole array, sort it out later */
+ for (i = 0; i < num_items; i++) {
+ size_t read_length = min_t(size_t, item_length,
+ sizeof(union viommu_topo_cfg));
+
+ viommu_ccopy((__le32 *)&viommu_spec->cfg[i],
+ (void __iomem *)cfg + offset,
+ read_length);
+
+ offset += item_length;
+ }
+ viommu_spec->num_items = num_items;
+
+ mutex_lock(&viommus_lock);
+ list_add(&viommu_spec->list, &viommus);
+ mutex_unlock(&viommus_lock);
+
+ return 0;
+}
+
+static void viommu_pci_parse_topology(struct pci_dev *dev)
+{
+ int pos;
+ u32 features;
+ void __iomem *regs;
+ struct viommu_cap_config cap = {0};
+ struct virtio_pci_common_cfg __iomem *common_cfg;
+
+ /*
+ * The virtio infrastructure might not be loaded at this point. we need
+ * to access the BARs ourselves.
+ */
+ pos = viommu_pci_find_capability(dev, VIRTIO_PCI_CAP_COMMON_CFG, &cap);
+ if (!pos) {
+ pci_warn(dev, "common capability not found\n");
+ return;
+ }
+
+ if (pci_enable_device_mem(dev))
+ return;
+
+ regs = pci_iomap(dev, cap.bar, 0);
+ if (!regs)
+ return;
+
+ common_cfg = regs + cap.offset;
+
+ /* Find out if the device supports topology description */
+ writel(0, &common_cfg->device_feature_select);
+ features = ioread32(&common_cfg->device_feature);
+
+ pci_iounmap(dev, regs);
+
+ if (!(features & BIT(VIRTIO_IOMMU_F_TOPOLOGY))) {
+ pci_dbg(dev, "device doesn't have topology description");
+ return;
+ }
+
+ pos = viommu_pci_find_capability(dev, VIRTIO_PCI_CAP_DEVICE_CFG, &cap);
+ if (!pos) {
+ pci_warn(dev, "device config capability not found\n");
+ return;
+ }
+
+ regs = pci_iomap(dev, cap.bar, 0);
+ if (!regs)
+ return;
+
+ pci_info(dev, "parsing virtio-iommu topology\n");
+ viommu_parse_topology(&dev->dev, regs + cap.offset);
+ pci_iounmap(dev, regs);
+}
+
+/*
+ * Catch a PCI virtio-iommu implementation early to get the topology
description
+ * before we start probing other endpoints.
+ */
+DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_REDHAT_QUMRANET, 0x1040 +
VIRTIO_ID_IOMMU,
+ viommu_pci_parse_topology);
+
+/*
+ * Return true if the device matches this topology structure. Write the
endpoint
+ * ID into epid if it's the case.
+ */
+static bool viommu_parse_pci(struct pci_dev *pdev, union viommu_topo_cfg *cfg,
+ u32 *epid)
+{
+ u32 endpoint_start;
+ u16 start, end, domain;
+ u16 devid = pci_dev_id(pdev);
+ u16 type = le16_to_cpu(cfg->type);
+
+ if (type != VIRTIO_IOMMU_TOPO_PCI_RANGE)
+ return false;
+
+ start = le16_to_cpu(cfg->pci.requester_start);
+ end = le16_to_cpu(cfg->pci.requester_end);
+ domain = le16_to_cpu(cfg->pci.hierarchy);
+ endpoint_start = le32_to_cpu(cfg->pci.endpoint_start);
+
+ if (pci_domain_nr(pdev->bus) == domain &&
+ devid >= start && devid <= end) {
+ *epid = devid - start + endpoint_start;
+ return true;
+ }
+ return false;
+}
+
+static const struct iommu_ops *virt_iommu_setup(struct device *dev)
+{
+ struct iommu_fwspec *fwspec = dev_iommu_fwspec_get(dev);
+ const struct iommu_ops *viommu_ops = NULL;
+ struct fwnode_handle *viommu_fwnode;
+ struct viommu_spec *viommu_spec;
+ struct pci_dev *pci_dev = NULL;
+ struct device *viommu_dev;
+ bool found = false;
+ size_t i;
+ u32 epid;
+ int ret;
+
+ /* Already translated? */
+ if (fwspec && fwspec->ops)
+ return fwspec->ops;
+
+ if (dev_is_pci(dev)) {
+ pci_dev = to_pci_dev(dev);
+ } else {
+ /* At the moment we don't support platform devices */
+ return NULL;
+ }
+
+ mutex_lock(&viommus_lock);
+ list_for_each_entry(viommu_spec, &viommus, list) {
+ for (i = 0; i < viommu_spec->num_items; i++) {
+ union viommu_topo_cfg *cfg = &viommu_spec->cfg[i];
+
+ found = viommu_parse_pci(pci_dev, cfg, &epid);
+ if (found)
+ break;
+ }
+ if (found) {
+ viommu_ops = viommu_spec->ops;
+ viommu_fwnode = viommu_spec->fwnode;
+ viommu_dev = viommu_spec->dev;
+ break;
+ }
+ }
+ mutex_unlock(&viommus_lock);
+ if (!found)
+ return NULL;
+
+ /* We're not translating ourselves. */
+ if (viommu_dev == dev)
+ return NULL;
+
+ /*
+ * If we found a PCI range managed by the viommu, we're the ones that
+ * have to request ACS.
+ */
+ if (pci_dev)
+ pci_request_acs();
+
+ if (!viommu_ops)
+ return ERR_PTR(-EPROBE_DEFER);
+
+ ret = iommu_fwspec_init(dev, viommu_fwnode, viommu_ops);
+ if (ret)
+ return ERR_PTR(ret);
+
+ iommu_fwspec_add_ids(dev, &epid, 1);
+
+ return viommu_ops;
+}
+
+/**
+ * virt_dma_configure - Configure DMA of virtualized devices
+ * @dev: the endpoint
+ *
+ * Setup the DMA and IOMMU ops of a virtual device, for platforms without DT or
+ * ACPI.
+ *
+ * Return: -EPROBE_DEFER if the device is managed by an IOMMU that hasn't
been
+ * probed yet, 0 otherwise
+ */
+int virt_dma_configure(struct device *dev)
+{
+ const struct iommu_ops *iommu_ops;
+
+ iommu_ops = virt_iommu_setup(dev);
+ if (IS_ERR_OR_NULL(iommu_ops)) {
+ int ret = PTR_ERR(iommu_ops);
+
+ if (ret == -EPROBE_DEFER || ret == 0)
+ return ret;
+ dev_err(dev, "error %d while setting up virt IOMMU\n", ret);
+ return 0;
+ }
+
+ /*
+ * If we have reason to believe the IOMMU driver missed the initial
+ * add_device callback for dev, replay it to get things in order.
+ */
+ if (dev->bus && !device_iommu_mapped(dev))
+ iommu_probe_device(dev);
+
+ /* Assume coherent, as well as full 64-bit addresses. */
+#ifdef CONFIG_ARCH_HAS_SETUP_DMA_OPS
+ arch_setup_dma_ops(dev, 0, ~0ULL, iommu_ops, true);
+#else
+ iommu_setup_dma_ops(dev, 0, ~0ULL);
+#endif
+ return 0;
+}
+
+/**
+ * virt_set_iommu_ops - Set the IOMMU ops of a virtual IOMMU device
+ * @dev: the IOMMU device (transport)
+ * @ops: the new IOMMU ops or NULL
+ *
+ * Setup the iommu_ops associated to a viommu_spec, once the driver is loaded
+ * and the device probed.
+ */
+void virt_set_iommu_ops(struct device *dev, struct iommu_ops *ops)
+{
+ struct viommu_spec *viommu_spec;
+
+ mutex_lock(&viommus_lock);
+ list_for_each_entry(viommu_spec, &viommus, list) {
+ if (viommu_spec->dev == dev) {
+ viommu_spec->ops = ops;
+ viommu_spec->fwnode = ops ? dev->fwnode : NULL;
+ break;
+ }
+ }
+ mutex_unlock(&viommus_lock);
+}
+EXPORT_SYMBOL_GPL(virt_set_iommu_ops);
diff --git a/drivers/iommu/virtio-iommu.c b/drivers/iommu/virtio-iommu.c
index cce329d71fba..f18ba8e22ebd 100644
--- a/drivers/iommu/virtio-iommu.c
+++ b/drivers/iommu/virtio-iommu.c
@@ -21,6 +21,7 @@
#include <linux/virtio.h>
#include <linux/virtio_config.h>
#include <linux/virtio_ids.h>
+#include <linux/virt_iommu.h>
#include <linux/wait.h>
#include <uapi/linux/virtio_iommu.h>
@@ -1075,6 +1076,7 @@ static int viommu_probe(struct virtio_device *vdev)
if (ret)
goto err_free_vqs;
+ virt_set_iommu_ops(dev->parent, &viommu_ops);
iommu_device_set_ops(&viommu->iommu, &viommu_ops);
iommu_device_set_fwnode(&viommu->iommu, parent_dev->fwnode);
@@ -1122,6 +1124,7 @@ static void viommu_remove(struct virtio_device *vdev)
{
struct viommu_dev *viommu = vdev->priv;
+ virt_set_iommu_ops(vdev->dev.parent, NULL);
iommu_device_sysfs_remove(&viommu->iommu);
iommu_device_unregister(&viommu->iommu);
diff --git a/include/linux/virt_iommu.h b/include/linux/virt_iommu.h
new file mode 100644
index 000000000000..c68b03ec75ba
--- /dev/null
+++ b/include/linux/virt_iommu.h
@@ -0,0 +1,19 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef VIRTIO_IOMMU_H_
+#define VIRTIO_IOMMU_H_
+
+#if IS_ENABLED(CONFIG_VIRTIO_IOMMU_TOPOLOGY)
+int virt_dma_configure(struct device *dev);
+void virt_set_iommu_ops(struct device *dev, struct iommu_ops *ops);
+#else /* !CONFIG_VIRTIO_IOMMU_TOPOLOGY */
+static inline int virt_dma_configure(struct device *dev)
+{
+ /* Don't disturb the normal DMA configuration methods */
+ return 0;
+}
+
+static inline void virt_set_iommu_ops(struct device *dev, struct iommu_ops
*ops)
+{ }
+#endif /* !CONFIG_VIRTIO_IOMMU_TOPOLOGY */
+
+#endif /* VIRTIO_IOMMU_H_ */
diff --git a/include/uapi/linux/virtio_iommu.h
b/include/uapi/linux/virtio_iommu.h
index 237e36a280cb..ec57d215086a 100644
--- a/include/uapi/linux/virtio_iommu.h
+++ b/include/uapi/linux/virtio_iommu.h
@@ -16,6 +16,7 @@
#define VIRTIO_IOMMU_F_BYPASS 3
#define VIRTIO_IOMMU_F_PROBE 4
#define VIRTIO_IOMMU_F_MMIO 5
+#define VIRTIO_IOMMU_F_TOPOLOGY 6
struct virtio_iommu_range_64 {
__le64 start;
@@ -27,6 +28,12 @@ struct virtio_iommu_range_32 {
__le32 end;
};
+struct virtio_iommu_topo_config {
+ __le32 offset;
+ __le32 num_items;
+ __le32 item_length;
+};
+
struct virtio_iommu_config {
/* Supported page sizes */
__le64 page_size_mask;
@@ -36,6 +43,25 @@ struct virtio_iommu_config {
struct virtio_iommu_range_32 domain_range;
/* Probe buffer size */
__le32 probe_size;
+ struct virtio_iommu_topo_config topo_config;
+};
+
+#define VIRTIO_IOMMU_TOPO_PCI_RANGE 0x1
+#define VIRTIO_IOMMU_TOPO_ENDPOINT 0x2
+
+struct virtio_iommu_topo_pci_range {
+ __le16 type;
+ __le16 hierarchy;
+ __le16 requester_start;
+ __le16 requester_end;
+ __le32 endpoint_start;
+};
+
+struct virtio_iommu_topo_endpoint {
+ __le16 type;
+ __le16 reserved;
+ __le32 endpoint;
+ __le64 address;
};
/* Request types */
--
2.25.0
Jean-Philippe Brucker
2020-Feb-14 16:04 UTC
[PATCH 2/3] PCI: Add DMA configuration for virtual platforms
Hardware platforms usually describe the IOMMU topology using either device-tree pointers or vendor-specific ACPI tables. For virtual platforms that don't provide a device-tree, the virtio-iommu device contains a description of the endpoints it manages. That information allows us to probe endpoints after the IOMMU is probed (possibly as late as userspace modprobe), provided it is discovered early enough. Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the endpoint is managed by a vIOMMU that will be loaded later, or 0 in any other case to avoid disturbing the normal DMA configuration methods. When CONFIG_VIRTIO_IOMMU_TOPOLOGY isn't selected, the call to virt_dma_configure() is compiled out. As long as the information is consistent, platforms can provide both a device-tree and a built-in topology, and the IOMMU infrastructure is able to deal with multiple DMA configuration methods. Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org> --- drivers/pci/pci-driver.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 0454ca0e4e3f..69303a814f21 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -18,6 +18,7 @@ #include <linux/kexec.h> #include <linux/of_device.h> #include <linux/acpi.h> +#include <linux/virt_iommu.h> #include "pci.h" #include "pcie/portdrv.h" @@ -1602,6 +1603,10 @@ static int pci_dma_configure(struct device *dev) struct device *bridge; int ret = 0; + ret = virt_dma_configure(dev); + if (ret) + return ret; + bridge = pci_get_host_bridge_device(to_pci_dev(dev)); if (IS_ENABLED(CONFIG_OF) && bridge->parent && -- 2.25.0
With the built-in topology description in place, x86 platforms can now use the virtio-iommu. Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org> --- drivers/iommu/Kconfig | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig index 068d4e0e3541..adcbda44d473 100644 --- a/drivers/iommu/Kconfig +++ b/drivers/iommu/Kconfig @@ -508,8 +508,9 @@ config HYPERV_IOMMU config VIRTIO_IOMMU bool "Virtio IOMMU driver" depends on VIRTIO=y - depends on ARM64 + depends on (ARM64 || X86) select IOMMU_API + select IOMMU_DMA select INTERVAL_TREE help Para-virtualised IOMMU driver with virtio. -- 2.25.0
On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:> With the built-in topology description in place, x86 platforms can now > use the virtio-iommu. > > Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org> > --- > drivers/iommu/Kconfig | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig > index 068d4e0e3541..adcbda44d473 100644 > --- a/drivers/iommu/Kconfig > +++ b/drivers/iommu/Kconfig > @@ -508,8 +508,9 @@ config HYPERV_IOMMU > config VIRTIO_IOMMU > bool "Virtio IOMMU driver" > depends on VIRTIO=y > - depends on ARM64 > + depends on (ARM64 || X86) > select IOMMU_API > + select IOMMU_DMACan that have an "if X86" for clarity? AIUI it's not necessary for virtio-iommu itself (and really shouldn't be), but is merely to satisfy the x86 arch code's expectation that IOMMU drivers bring their own DMA ops, right? Robin.> select INTERVAL_TREE > help > Para-virtualised IOMMU driver with virtio. >
Robin Murphy
2020-Feb-14 17:03 UTC
[PATCH 2/3] PCI: Add DMA configuration for virtual platforms
On 14/02/2020 4:04 pm, Jean-Philippe Brucker wrote:> Hardware platforms usually describe the IOMMU topology using either > device-tree pointers or vendor-specific ACPI tables. For virtual > platforms that don't provide a device-tree, the virtio-iommu device > contains a description of the endpoints it manages. That information > allows us to probe endpoints after the IOMMU is probed (possibly as late > as userspace modprobe), provided it is discovered early enough. > > Add a hook to pci_dma_configure(), which returns -EPROBE_DEFER if the > endpoint is managed by a vIOMMU that will be loaded later, or 0 in any > other case to avoid disturbing the normal DMA configuration methods. > When CONFIG_VIRTIO_IOMMU_TOPOLOGY isn't selected, the call to > virt_dma_configure() is compiled out. > > As long as the information is consistent, platforms can provide both a > device-tree and a built-in topology, and the IOMMU infrastructure is > able to deal with multiple DMA configuration methods.Urgh, it's already been established[1] that having IOMMU setup tied to DMA configuration at driver probe time is not just conceptually wrong but actually broken, so the concept here worries me a bit. In a world where of_iommu_configure() and friends are being called much earlier around iommu_probe_device() time, how badly will this fall apart? Robin. [1] https://lore.kernel.org/linux-iommu/9625faf4-48ef-2dd3-d82f-931d9cf26976 at huawei.com/> Signed-off-by: Jean-Philippe Brucker <jean-philippe at linaro.org> > --- > drivers/pci/pci-driver.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 0454ca0e4e3f..69303a814f21 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -18,6 +18,7 @@ > #include <linux/kexec.h> > #include <linux/of_device.h> > #include <linux/acpi.h> > +#include <linux/virt_iommu.h> > #include "pci.h" > #include "pcie/portdrv.h" > > @@ -1602,6 +1603,10 @@ static int pci_dma_configure(struct device *dev) > struct device *bridge; > int ret = 0; > > + ret = virt_dma_configure(dev); > + if (ret) > + return ret; > + > bridge = pci_get_host_bridge_device(to_pci_dev(dev)); > > if (IS_ENABLED(CONFIG_OF) && bridge->parent && >
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