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Subject[PATCH v9 06/11] vfio/pci: Allow to mmap the fault queue
Date
The DMA FAULT region contains the fault ring buffer.
There is benefit to let the userspace mmap this area.
Expose this mmappable area through a sparse mmap entry
and implement the mmap operation.

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

---

v8 -> v9:
- remove unused index local variable in vfio_pci_fault_mmap
---
drivers/vfio/pci/vfio_pci.c | 61 +++++++++++++++++++++++++++++++++++--
1 file changed, 58 insertions(+), 3 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
index c6fdbd64bfb2..7d62dcdbdf0b 100644
--- a/drivers/vfio/pci/vfio_pci.c
+++ b/drivers/vfio/pci/vfio_pci.c
@@ -264,21 +264,75 @@ static void vfio_pci_dma_fault_release(struct vfio_pci_device *vdev,
{
}

+static int vfio_pci_dma_fault_mmap(struct vfio_pci_device *vdev,
+ struct vfio_pci_region *region,
+ struct vm_area_struct *vma)
+{
+ u64 phys_len, req_len, pgoff, req_start;
+ unsigned long long addr;
+ unsigned int ret;
+
+ phys_len = region->size;
+
+ req_len = vma->vm_end - vma->vm_start;
+ pgoff = vma->vm_pgoff &
+ ((1U << (VFIO_PCI_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+ req_start = pgoff << PAGE_SHIFT;
+
+ /* only the second page of the producer fault region is mmappable */
+ if (req_start < PAGE_SIZE)
+ return -EINVAL;
+
+ if (req_start + req_len > phys_len)
+ return -EINVAL;
+
+ addr = virt_to_phys(vdev->fault_pages);
+ vma->vm_private_data = vdev;
+ vma->vm_pgoff = (addr >> PAGE_SHIFT) + pgoff;
+
+ ret = remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+ req_len, vma->vm_page_prot);
+ return ret;
+}
+
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_sparse_mmap *sparse = NULL;
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));
+ size_t size = sizeof(*sparse) + sizeof(*sparse->areas);
+ int ret;
+
+ ret = vfio_info_add_capability(caps, &cap.header, sizeof(cap));
+ if (ret)
+ return ret;
+
+ sparse = kzalloc(size, GFP_KERNEL);
+ if (!sparse)
+ return -ENOMEM;
+
+ sparse->header.id = VFIO_REGION_INFO_CAP_SPARSE_MMAP;
+ sparse->header.version = 1;
+ sparse->nr_areas = 1;
+ sparse->areas[0].offset = PAGE_SIZE;
+ sparse->areas[0].size = region->size - PAGE_SIZE;
+
+ ret = vfio_info_add_capability(caps, &sparse->header, size);
+ if (ret)
+ kfree(sparse);
+
+ return ret;
}

static const struct vfio_pci_regops vfio_pci_dma_fault_regops = {
.rw = vfio_pci_dma_fault_rw,
.release = vfio_pci_dma_fault_release,
+ .mmap = vfio_pci_dma_fault_mmap,
.add_capability = vfio_pci_dma_fault_add_capability,
};

@@ -339,7 +393,8 @@ static int vfio_pci_init_dma_fault_region(struct vfio_pci_device *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,
+ VFIO_REGION_INFO_FLAG_READ | VFIO_REGION_INFO_FLAG_WRITE |
+ VFIO_REGION_INFO_FLAG_MMAP,
vdev->fault_pages);
if (ret)
goto out;
@@ -347,7 +402,7 @@ static int vfio_pci_init_dma_fault_region(struct vfio_pci_device *vdev)
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);
+ header->offset = PAGE_SIZE;

ret = iommu_register_device_fault_handler(&vdev->pdev->dev,
vfio_pci_iommu_dev_fault_handler,
--
2.20.1
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