Linux-libre 4.4-gnupck-4.4-gnu

1 files changed, 14 insertions, 1 deletions

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 57d8c37a0..59d47cb63 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -403,13 +403,26 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
 static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
 {
 	struct vfio_domain *domain;
-	unsigned long bitmap = PAGE_MASK;
+	unsigned long bitmap = ULONG_MAX;
 
 	mutex_lock(&iommu->lock);
 	list_for_each_entry(domain, &iommu->domain_list, next)
 		bitmap &= domain->domain->ops->pgsize_bitmap;
 	mutex_unlock(&iommu->lock);
 
+	/*
+	 * In case the IOMMU supports page sizes smaller than PAGE_SIZE
+	 * we pretend PAGE_SIZE is supported and hide sub-PAGE_SIZE sizes.
+	 * That way the user will be able to map/unmap buffers whose size/
+	 * start address is aligned with PAGE_SIZE. Pinning code uses that
+	 * granularity while iommu driver can use the sub-PAGE_SIZE size
+	 * to map the buffer.
+	 */
+	if (bitmap & ~PAGE_MASK) {
+		bitmap &= PAGE_MASK;
+		bitmap |= PAGE_SIZE;
+	}
+
 	return bitmap;
 }