[PATCH v11 04/13] vfio/pci: Add VFIO_REGION_TYPE_NESTED region type

Eric Auger
2020-11-16T12:34:18Z

Add a new specific DMA_FAULT region aiming to exposed nested mode
translation faults. This region only is exposed if the device
is attached to a nested domain.

The region has a ring buffer that contains the actual fault
records plus a header allowing to handle it (tail/head indices,
max capacity, entry size). At the moment the region is dimensionned
for 512 fault records.

Signed-off-by: Eric Auger <eric.auger@redhat.com>

---
v11 -> v12:
- set fault_pages to NULL after free
- check new_tail >= header->nb_entries (Zenghui)

v10 -> v11:
- rename vfio_pci_init_dma_fault_region into
vfio_pci_dma_fault_init
- free fault_pages in vfio_pci_dma_fault_release
- only register the region if the device is attached
to a nested domain

v8 -> v9:
- Use a single region instead of a prod/cons region

v4 -> v5
- check cons is not null in vfio_pci_check_cons_fault

v3 -> v4:
- use 2 separate regions, respectively in read and write modes
- add the version capability
---
drivers/vfio/pci/vfio_pci.c | 76 +++++++++++++++++++++++++++++
drivers/vfio/pci/vfio_pci_private.h | 6 +++
drivers/vfio/pci/vfio_pci_rdwr.c | 44 +++++++++++++++++
include/uapi/linux/vfio.h | 34 +++++++++++++
4 files changed, 160 insertions(+)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index e6190173482c..7546a81e7fb6 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -311,6 +311,78 @@ int vfio_pci_set_power_state(struct vfio_pci_device *vdev, pci_power_t state)
return ret;
}

+static void vfio_pci_dma_fault_release(struct vfio_pci_device *vdev,
+ struct vfio_pci_region *region)
+{
+ kfree(vdev->fault_pages);
+}
+
+static int vfio_pci_dma_fault_add_capability(struct vfio_pci_device *vdev,
+ struct vfio_pci_region *region,
+ struct vfio_info_cap *caps)
+{
+ struct vfio_region_info_cap_fault cap = {
+ .header.id = VFIO_REGION_INFO_CAP_DMA_FAULT,
+ .header.version = 1,
+ .version = 1,
+ };
+ return vfio_info_add_capability(caps, &cap.header, sizeof(cap));
+}
+
+static const struct vfio_pci_regops vfio_pci_dma_fault_regops = {
+ .rw = vfio_pci_dma_fault_rw,
+ .release = vfio_pci_dma_fault_release,
+ .add_capability = vfio_pci_dma_fault_add_capability,
+};
+
+#define DMA_FAULT_RING_LENGTH 512
+
+static int vfio_pci_dma_fault_init(struct vfio_pci_device *vdev)
+{
+ struct vfio_region_dma_fault *header;
+ struct iommu_domain *domain;
+ size_t size;
+ bool nested;
+ int ret;
+
+ domain = iommu_get_domain_for_dev(&vdev->pdev->dev);
+ ret = iommu_domain_get_attr(domain, DOMAIN_ATTR_NESTING, &nested);
+ if (ret || !nested)
+ return ret;
+
+ mutex_init(&vdev->fault_queue_lock);
+
+ /*
+ * We provision 1 page for the header and space for
+ * DMA_FAULT_RING_LENGTH fault records in the ring buffer.
+ */
+ size = ALIGN(sizeof(struct iommu_fault) *
+ DMA_FAULT_RING_LENGTH, PAGE_SIZE) + PAGE_SIZE;
+
+ vdev->fault_pages = kzalloc(size, GFP_KERNEL);
+ if (!vdev->fault_pages)
+ return -ENOMEM;
+
+ ret = vfio_pci_register_dev_region(vdev,
+ VFIO_REGION_TYPE_NESTED,
+ VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT,
+ &vfio_pci_dma_fault_regops, size,
+ VFIO_REGION_INFO_FLAG_READ | VFIO_REGION_INFO_FLAG_WRITE,
+ vdev->fault_pages);
+ if (ret)
+ goto out;
+
+ header = (struct vfio_region_dma_fault *)vdev->fault_pages;
+ header->entry_size = sizeof(struct iommu_fault);
+ header->nb_entries = DMA_FAULT_RING_LENGTH;
+ header->offset = sizeof(struct vfio_region_dma_fault);
+ return 0;
+out:
+ kfree(vdev->fault_pages);
+ vdev->fault_pages = NULL;
+ return ret;
+}
+
static int vfio_pci_enable(struct vfio_pci_device *vdev)
{
struct pci_dev *pdev = vdev->pdev;
@@ -409,6 +481,10 @@ static int vfio_pci_enable(struct vfio_pci_device *vdev)
}
}

+ ret = vfio_pci_dma_fault_init(vdev);
+ if (ret)
+ goto disable_exit;
+
vfio_pci_probe_mmaps(vdev);

return 0;
diff --git a/drivers/vfio/pci/vfio_pci_private.h b/drivers/vfio/pci/vfio_pci_private.h
index 5c90e560c5c7..1d9b0f648133 100644
--- a/drivers/vfio/pci/vfio_pci_private.h
+++ b/drivers/vfio/pci/vfio_pci_private.h
@@ -134,6 +134,8 @@ struct vfio_pci_device {
int ioeventfds_nr;
struct eventfd_ctx *err_trigger;
struct eventfd_ctx *req_trigger;
+ u8 *fault_pages;
+ struct mutex fault_queue_lock;
struct list_head dummy_resources_list;
struct mutex ioeventfds_lock;
struct list_head ioeventfds_list;
@@ -170,6 +172,10 @@ extern ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
extern long vfio_pci_ioeventfd(struct vfio_pci_device *vdev, loff_t offset,
uint64_t data, int count, int fd);

+extern size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev,
+ char __user *buf, size_t count,
+ loff_t *ppos, bool iswrite);
+
extern int vfio_pci_init_perm_bits(void);
extern void vfio_pci_uninit_perm_bits(void);

diff --git a/drivers/vfio/pci/vfio_pci_rdwr.c b/drivers/vfio/pci/vfio_pci_rdwr.c
index a0b5fc8e46f4..164120607469 100644
--- a/drivers/vfio/pci/vfio_pci_rdwr.c
+++ b/drivers/vfio/pci/vfio_pci_rdwr.c
@@ -356,6 +356,50 @@ ssize_t vfio_pci_vga_rw(struct vfio_pci_device *vdev, char __user *buf,
return done;
}

+size_t vfio_pci_dma_fault_rw(struct vfio_pci_device *vdev, char __user *buf,
+ size_t count, loff_t *ppos, bool iswrite)
+{
+ unsigned int i = VFIO_PCI_OFFSET_TO_INDEX(*ppos) - VFIO_PCI_NUM_REGIONS;
+ loff_t pos = *ppos & VFIO_PCI_OFFSET_MASK;
+ void *base = vdev->region[i].data;
+ int ret = -EFAULT;
+
+ if (pos >= vdev->region[i].size)
+ return -EINVAL;
+
+ count = min(count, (size_t)(vdev->region[i].size - pos));
+
+ mutex_lock(&vdev->fault_queue_lock);
+
+ if (iswrite) {
+ struct vfio_region_dma_fault *header =
+ (struct vfio_region_dma_fault *)base;
+ u32 new_tail;
+
+ if (pos != 0 || count != 4) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+
+ if (copy_from_user((void *)&new_tail, buf, count))
+ goto unlock;
+
+ if (new_tail >= header->nb_entries) {
+ ret = -EINVAL;
+ goto unlock;
+ }
+ header->tail = new_tail;
+ } else {
+ if (copy_to_user(buf, base + pos, count))
+ goto unlock;
+ }
+ *ppos += count;
+ ret = count;
+unlock:
+ mutex_unlock(&vdev->fault_queue_lock);
+ return ret;
+}
+
static void vfio_pci_ioeventfd_do_write(struct vfio_pci_ioeventfd *ioeventfd,
bool test_mem)
{
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index b352e76cfb71..629dfb38d9e7 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -343,6 +343,9 @@ struct vfio_region_info_cap_type {
/* sub-types for VFIO_REGION_TYPE_GFX */
#define VFIO_REGION_SUBTYPE_GFX_EDID (1)

+#define VFIO_REGION_TYPE_NESTED (2)
+#define VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT (1)
+
/**
* struct vfio_region_gfx_edid - EDID region layout.
*
@@ -988,6 +991,37 @@ struct vfio_device_feature {
*/
#define VFIO_DEVICE_FEATURE_PCI_VF_TOKEN (0)

+/*
+ * Capability exposed by the DMA fault region
+ * @version: ABI version
+ */
+#define VFIO_REGION_INFO_CAP_DMA_FAULT 6
+
+struct vfio_region_info_cap_fault {
+ struct vfio_info_cap_header header;
+ __u32 version;
+};
+
+/*
+ * DMA Fault Region Layout
+ * @tail: index relative to the start of the ring buffer at which the
+ * consumer finds the next item in the buffer
+ * @entry_size: fault ring buffer entry size in bytes
+ * @nb_entries: max capacity of the fault ring buffer
+ * @offset: ring buffer offset relative to the start of the region
+ * @head: index relative to the start of the ring buffer at which the
+ * producer (kernel) inserts items into the buffers
+ */
+struct vfio_region_dma_fault {
+ /* Write-Only */
+ __u32 tail;
+ /* Read-Only */
+ __u32 entry_size;
+ __u32 nb_entries;
+ __u32 offset;
+ __u32 head;
+};
+
/* -------- API for Type1 VFIO IOMMU -------- */

/**
--
2.21.3