vfio iommu: Update UNMAP_DMA ioctl to get dirty bitmap before unmap

DMA mapped pages, including those pinned by mdev vendor drivers, might
get unpinned and unmapped while migration is active and device is still
running. For example, in pre-copy phase while guest driver could access
those pages, host device or vendor driver can dirty these mapped pages.
Such pages should be marked dirty so as to maintain memory consistency
for a user making use of dirty page tracking.

To get bitmap during unmap, user should allocate memory for bitmap, set
it all zeros, set size of allocated memory, set page size to be
considered for bitmap and set flag VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP.

Signed-off-by: Kirti Wankhede <kwankhede@nvidia.com>
Reviewed-by: Neo Jia <cjia@nvidia.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Reviewed-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

1 files changed, 50 insertions, 11 deletions

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index be6fc0d88633..e31fcc23e81a 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -1049,23 +1049,25 @@ static int verify_bitmap_size(uint64_t npages, uint64_t bitmap_size)
 }
 
 static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
-			     struct vfio_iommu_type1_dma_unmap *unmap)
+			     struct vfio_iommu_type1_dma_unmap *unmap,
+			     struct vfio_bitmap *bitmap)
 {
-	uint64_t mask;
 	struct vfio_dma *dma, *dma_last = NULL;
-	size_t unmapped = 0;
+	size_t unmapped = 0, pgsize;
 	int ret = 0, retries = 0;
+	unsigned long pgshift;
 
 	mutex_lock(&iommu->lock);
 
-	mask = ((uint64_t)1 << __ffs(iommu->pgsize_bitmap)) - 1;
+	pgshift = __ffs(iommu->pgsize_bitmap);
+	pgsize = (size_t)1 << pgshift;
 
-	if (unmap->iova & mask) {
+	if (unmap->iova & (pgsize - 1)) {
 		ret = -EINVAL;
 		goto unlock;
 	}
 
-	if (!unmap->size || unmap->size & mask) {
+	if (!unmap->size || unmap->size & (pgsize - 1)) {
 		ret = -EINVAL;
 		goto unlock;
 	}
@@ -1076,9 +1078,15 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 		goto unlock;
 	}
 
-	WARN_ON(mask & PAGE_MASK);
-again:
+	/* When dirty tracking is enabled, allow only min supported pgsize */
+	if ((unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) &&
+	    (!iommu->dirty_page_tracking || (bitmap->pgsize != pgsize))) {
+		ret = -EINVAL;
+		goto unlock;
+	}
 
+	WARN_ON((pgsize - 1) & PAGE_MASK);
+again:
 	/*
 	 * vfio-iommu-type1 (v1) - User mappings were coalesced together to
 	 * avoid tracking individual mappings.  This means that the granularity
@@ -1159,6 +1167,14 @@ again:
 			mutex_lock(&iommu->lock);
 			goto again;
 		}
+
+		if (unmap->flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) {
+			ret = update_user_bitmap(bitmap->data, dma,
+						 unmap->iova, pgsize);
+			if (ret)
+				break;
+		}
+
 		unmapped += dma->size;
 		vfio_remove_dma(iommu, dma);
 	}
@@ -2497,17 +2513,40 @@ static long vfio_iommu_type1_ioctl(void *iommu_data,
 
 	} else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
 		struct vfio_iommu_type1_dma_unmap unmap;
-		long ret;
+		struct vfio_bitmap bitmap = { 0 };
+		int ret;
 
 		minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);
 
 		if (copy_from_user(&unmap, (void __user *)arg, minsz))
 			return -EFAULT;
 
-		if (unmap.argsz < minsz || unmap.flags)
+		if (unmap.argsz < minsz ||
+		    unmap.flags & ~VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP)
 			return -EINVAL;
 
-		ret = vfio_dma_do_unmap(iommu, &unmap);
+		if (unmap.flags & VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP) {
+			unsigned long pgshift;
+
+			if (unmap.argsz < (minsz + sizeof(bitmap)))
+				return -EINVAL;
+
+			if (copy_from_user(&bitmap,
+					   (void __user *)(arg + minsz),
+					   sizeof(bitmap)))
+				return -EFAULT;
+
+			if (!access_ok((void __user *)bitmap.data, bitmap.size))
+				return -EINVAL;
+
+			pgshift = __ffs(bitmap.pgsize);
+			ret = verify_bitmap_size(unmap.size >> pgshift,
+						 bitmap.size);
+			if (ret)
+				return ret;
+		}
+
+		ret = vfio_dma_do_unmap(iommu, &unmap, &bitmap);
 		if (ret)
 			return ret;