[PATCH V3 4/9] vfio: interfaces to update vaddr

[Steve Sistare <steven.sistare@oracle.com>]

Define interfaces that allow the underlying memory object of an iova
range to be mapped to a new host virtual address in the host process:

  - VFIO_DMA_UNMAP_FLAG_VADDR for VFIO_IOMMU_UNMAP_DMA
  - VFIO_DMA_MAP_FLAG_VADDR flag for VFIO_IOMMU_MAP_DMA
  - VFIO_UPDATE_VADDR extension for VFIO_CHECK_EXTENSION

Unmap vaddr invalidates the host virtual address in an iova range, and
blocks vfio translation of host virtual addresses.  DMA to already-mapped
pages continues.  Map vaddr updates the base VA and resumes translation.
See comments in uapi/linux/vfio.h for more details.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 include/uapi/linux/vfio.h | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 55578b6..85bb89a 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -49,6 +49,9 @@
 /* Supports VFIO_DMA_UNMAP_FLAG_ALL */
 #define VFIO_UNMAP_ALL			9
 
+/* Supports the vaddr flag for DMA map and unmap */
+#define VFIO_UPDATE_VADDR		10
+
 /*
  * The IOCTL interface is designed for extensibility by embedding the
  * structure length (argsz) and flags into structures passed between
@@ -1049,12 +1052,22 @@ struct vfio_iommu_type1_info_cap_migration {
  *
  * Map process virtual addresses to IO virtual addresses using the
  * provided struct vfio_dma_map. Caller sets argsz. READ &/ WRITE required.
+ *
+ * If flags & VFIO_DMA_MAP_FLAG_VADDR, update the base vaddr for iova, and
+ * unblock translation of host virtual addresses in the iova range.  The vaddr
+ * must have previously been invalidated with VFIO_DMA_UNMAP_FLAG_VADDR.  To
+ * maintain memory consistency within the user application, the updated vaddr
+ * must address the same memory object as originally mapped.  Failure to do so
+ * will result in user memory corruption and/or device misbehavior.  iova and
+ * size must match those in the original MAP_DMA call.  Protection is not
+ * changed, and the READ & WRITE flags must be 0.
  */
 struct vfio_iommu_type1_dma_map {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_DMA_MAP_FLAG_READ (1 << 0)		/* readable from device */
 #define VFIO_DMA_MAP_FLAG_WRITE (1 << 1)	/* writable from device */
+#define VFIO_DMA_MAP_FLAG_VADDR (1 << 2)
 	__u64	vaddr;				/* Process virtual address */
 	__u64	iova;				/* IO virtual address */
 	__u64	size;				/* Size of mapping (bytes) */
@@ -1090,12 +1103,18 @@ struct vfio_bitmap {
  *
  * If flags & VFIO_DMA_UNMAP_FLAG_ALL, unmap all addresses.  iova and size
  * must be 0.  This may not be combined with the get-dirty-bitmap flag.
+ *
+ * If flags & VFIO_DMA_UNMAP_FLAG_VADDR, do not unmap, but invalidate host
+ * virtual addresses in the iova range.  Tasks that attempt to translate an
+ * iova's vaddr will block.  DMA to already-mapped pages continues.  This may
+ * not be combined with the get-dirty-bitmap flag.
  */
 struct vfio_iommu_type1_dma_unmap {
 	__u32	argsz;
 	__u32	flags;
 #define VFIO_DMA_UNMAP_FLAG_GET_DIRTY_BITMAP (1 << 0)
 #define VFIO_DMA_UNMAP_FLAG_ALL		     (1 << 1)
+#define VFIO_DMA_UNMAP_FLAG_VADDR	     (1 << 2)
 	__u64	iova;				/* IO virtual address */
 	__u64	size;				/* Size of mapping (bytes) */
 	__u8    data[];
-- 
1.8.3.1