[PATCH 6/9] VFIO_PLATFORM: Support MMAP of MMIO regions

[Antonios Motakis]

Allow to memory map the MMIO regions of the device so userspace can
directly access them.

Signed-off-by: Antonios Motakis <a.mota...@virtualopensystems.com>
Tested-by: Alvise Rigo <a.r...@virtualopensystems.com>
---
 drivers/vfio/platform/vfio_platform.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/vfio/platform/vfio_platform.c 
b/drivers/vfio/platform/vfio_platform.c
index d0b2941..9786660 100644
--- a/drivers/vfio/platform/vfio_platform.c
+++ b/drivers/vfio/platform/vfio_platform.c
@@ -58,6 +58,11 @@ static int vfio_platform_regions_init(struct 
vfio_platform_device *vdev)
                region.flags = VFIO_REGION_INFO_FLAG_READ
                                | VFIO_REGION_INFO_FLAG_WRITE;
 
+               /* Only regions addressed with PAGE granularity can be MMAPed
+                * securely. */
+               if (!(region.addr & ~PAGE_MASK) && !(region.size & ~PAGE_MASK))
+                       region.flags |= VFIO_REGION_INFO_FLAG_MMAP;
+
                vdev->region[i] = region;
        }
 
@@ -283,6 +288,34 @@ err:
 
 static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma)
 {
+       struct vfio_platform_device *vdev = device_data;
+       u64 req_len = vma->vm_end - vma->vm_start;
+       u64 addr = vma->vm_pgoff << PAGE_SHIFT;
+       int i;
+
+       if (vma->vm_end < vma->vm_start)
+               return -EINVAL;
+       if (vma->vm_start & ~PAGE_MASK)
+               return -EINVAL;
+       if (vma->vm_end & ~PAGE_MASK)
+               return -EINVAL;
+       if ((vma->vm_flags & VM_SHARED) == 0)
+               return -EINVAL;
+
+       for (i = 0; i < vdev->num_regions; i++) {
+               struct vfio_platform_region region = vdev->region[i];
+
+               if ((addr < region.addr)
+                    || (addr + req_len - 1) >= (region.addr + region.size))
+                       continue;
+
+               vma->vm_private_data = vdev;
+               vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+               return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+                                      req_len, vma->vm_page_prot);
+       }
+
        return -EINVAL;
 }
 
-- 
1.8.3.2

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