iommufd: File mappings for mdev

Support file mappings for mediated devices, aka mdevs.  Access is
initiated by the vfio_pin_pages() and vfio_dma_rw() kernel interfaces.

Link: https://patch.msgid.link/r/[email protected]
Signed-off-by: Steve Sistare <[email protected]>
Reviewed-by: Jason Gunthorpe <[email protected]>
Reviewed-by: Kevin Tian <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>

Author: Steve Sistare

drivers/iommu/iommufd/pages.c

@@ -1814,11 +1814,11 @@ static int iopt_pages_fill_from_domain(struct iopt_pages *pages,
 	return 0;
 }
 
-static int iopt_pages_fill_from_mm(struct iopt_pages *pages,
-				   struct pfn_reader_user *user,
-				   unsigned long start_index,
-				   unsigned long last_index,
-				   struct page **out_pages)
+static int iopt_pages_fill(struct iopt_pages *pages,
+			   struct pfn_reader_user *user,
+			   unsigned long start_index,
+			   unsigned long last_index,
+			   struct page **out_pages)
 {
 	unsigned long cur_index = start_index;
 	int rc;
@@ -1892,8 +1892,8 @@ int iopt_pages_fill_xarray(struct iopt_pages *pages, unsigned long start_index,
 
 		/* hole */
 		cur_pages = out_pages + (span.start_hole - start_index);
-		rc = iopt_pages_fill_from_mm(pages, &user, span.start_hole,
-					     span.last_hole, cur_pages);
+		rc = iopt_pages_fill(pages, &user, span.start_hole,
+				     span.last_hole, cur_pages);
 		if (rc)
 			goto out_clean_xa;
 		rc = pages_to_xarray(&pages->pinned_pfns, span.start_hole,
@@ -1973,6 +1973,10 @@ static int iopt_pages_rw_page(struct iopt_pages *pages, unsigned long index,
 	struct page *page = NULL;
 	int rc;
 
+	if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
+	    WARN_ON(pages->type != IOPT_ADDRESS_USER))
+		return -EINVAL;
+
 	if (!mmget_not_zero(pages->source_mm))
 		return iopt_pages_rw_slow(pages, index, index, offset, data,
 					  length, flags);
@@ -2028,6 +2032,15 @@ int iopt_pages_rw_access(struct iopt_pages *pages, unsigned long start_byte,
 	if ((flags & IOMMUFD_ACCESS_RW_WRITE) && !pages->writable)
 		return -EPERM;
 
+	if (pages->type == IOPT_ADDRESS_FILE)
+		return iopt_pages_rw_slow(pages, start_index, last_index,
+					  start_byte % PAGE_SIZE, data, length,
+					  flags);
+
+	if (IS_ENABLED(CONFIG_IOMMUFD_TEST) &&
+	    WARN_ON(pages->type != IOPT_ADDRESS_USER))
+		return -EINVAL;
+
 	if (!(flags & IOMMUFD_ACCESS_RW_KTHREAD) && change_mm) {
 		if (start_index == last_index)
 			return iopt_pages_rw_page(pages, start_index,