vfio/platform: support MMAP of MMIO regions

Allow to memory map the MMIO regions of the device so userspace can
directly access them. PIO regions are not being handled at this point.

Signed-off-by: Antonios Motakis <a.motakis@virtualopensystems.com>
Signed-off-by: Baptiste Reynal <b.reynal@virtualopensystems.com>
Reviewed-by: Eric Auger <eric.auger@linaro.org>
Tested-by: Eric Auger <eric.auger@linaro.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 65 insertions, 0 deletions

diff --git a/drivers/vfio/platform/vfio_platform_common.c b/drivers/vfio/platform/vfio_platform_common.c
index 4df66f5fb313..d7fe2c71e8bc 100644
--- a/drivers/vfio/platform/vfio_platform_common.c
+++ b/drivers/vfio/platform/vfio_platform_common.c
@@ -55,6 +55,16 @@ static int vfio_platform_regions_init(struct vfio_platform_device *vdev)
 			if (!(res->flags & IORESOURCE_READONLY))
 				vdev->regions[i].flags |=
 					VFIO_REGION_INFO_FLAG_WRITE;
+
+			/*
+			 * Only regions addressed with PAGE granularity may be
+			 * MMAPed securely.
+			 */
+			if (!(vdev->regions[i].addr & ~PAGE_MASK) &&
+					!(vdev->regions[i].size & ~PAGE_MASK))
+				vdev->regions[i].flags |=
+					VFIO_REGION_INFO_FLAG_MMAP;
+
 			break;
 		case IORESOURCE_IO:
 			vdev->regions[i].type = VFIO_PLATFORM_REGION_TYPE_PIO;
@@ -334,8 +344,63 @@ static ssize_t vfio_platform_write(void *device_data, const char __user *buf,
 	return -EINVAL;
 }
 
+static int vfio_platform_mmap_mmio(struct vfio_platform_region region,
+				   struct vm_area_struct *vma)
+{
+	u64 req_len, pgoff, req_start;
+
+	req_len = vma->vm_end - vma->vm_start;
+	pgoff = vma->vm_pgoff &
+		((1U << (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT)) - 1);
+	req_start = pgoff << PAGE_SHIFT;
+
+	if (region.size < PAGE_SIZE || req_start + req_len > region.size)
+		return -EINVAL;
+
+	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+	vma->vm_pgoff = (region.addr >> PAGE_SHIFT) + pgoff;
+
+	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,
+			       req_len, vma->vm_page_prot);
+}
+
 static int vfio_platform_mmap(void *device_data, struct vm_area_struct *vma)
 {
+	struct vfio_platform_device *vdev = device_data;
+	unsigned int index;
+
+	index = vma->vm_pgoff >> (VFIO_PLATFORM_OFFSET_SHIFT - PAGE_SHIFT);
+
+	if (vma->vm_end < vma->vm_start)
+		return -EINVAL;
+	if (!(vma->vm_flags & VM_SHARED))
+		return -EINVAL;
+	if (index >= vdev->num_regions)
+		return -EINVAL;
+	if (vma->vm_start & ~PAGE_MASK)
+		return -EINVAL;
+	if (vma->vm_end & ~PAGE_MASK)
+		return -EINVAL;
+
+	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_MMAP))
+		return -EINVAL;
+
+	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_READ)
+			&& (vma->vm_flags & VM_READ))
+		return -EINVAL;
+
+	if (!(vdev->regions[index].flags & VFIO_REGION_INFO_FLAG_WRITE)
+			&& (vma->vm_flags & VM_WRITE))
+		return -EINVAL;
+
+	vma->vm_private_data = vdev;
+
+	if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_MMIO)
+		return vfio_platform_mmap_mmio(vdev->regions[index], vma);
+
+	else if (vdev->regions[index].type & VFIO_PLATFORM_REGION_TYPE_PIO)
+		return -EINVAL; /* not implemented */
+
 	return -EINVAL;
 }