i915_gem_do_execbuffer() holds the pages backing each relocation region for

various reasons while executing user commands.  After these commands are
completed, the pages backing the relocation regions are unheld.

Since relocation regions do not have to be page aligned, the code in
validate_exec_list() allocates 2 extra page pointers in the array of
held pages populated by vm_fault_quick_hold_pages().  However, the cleanup
code that unheld the pages always assumed that only the buffer size /
PAGE_SIZE pages were used.  This meant that non-page aligned buffers would
not unheld the last 1 or 2 pages in the list.  Fix this by saving the
number of held pages returned by vm_fault_quick_hold_pages() for each
relocation region and using this count during cleanup.

Reviewed by:	dumbbell, kib
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D3965

1 files changed, 12 insertions, 9 deletions

diff --git a/sys/dev/drm2/i915/i915_gem_execbuffer.c b/sys/dev/drm2/i915/i915_gem_execbuffer.c
index 088043d1a5c8..818efbf144ff 100644
--- a/sys/dev/drm2/i915/i915_gem_execbuffer.c
+++ b/sys/dev/drm2/i915/i915_gem_execbuffer.c
@@ -941,13 +941,15 @@ i915_gem_check_execbuffer(struct drm_i915_gem_execbuffer2 *exec)
 
 static int
 validate_exec_list(struct drm_i915_gem_exec_object2 *exec, int count,
-    vm_page_t ***map)
+    vm_page_t ***map, int **maplen)
 {
 	vm_page_t *ma;
 	int i, length, page_count;
 
 	/* XXXKIB various limits checking is missing there */
 	*map = malloc(count * sizeof(*ma), DRM_I915_GEM, M_WAITOK | M_ZERO);
+	*maplen = malloc(count * sizeof(*maplen), DRM_I915_GEM, M_WAITOK |
+	    M_ZERO);
 	for (i = 0; i < count; i++) {
 		/* First check for malicious input causing overflow */
 		if (exec[i].relocation_count >
@@ -969,9 +971,10 @@ validate_exec_list(struct drm_i915_gem_exec_object2 *exec, int count,
 		page_count = howmany(length, PAGE_SIZE) + 2;
 		ma = (*map)[i] = malloc(page_count * sizeof(vm_page_t),
 		    DRM_I915_GEM, M_WAITOK | M_ZERO);
-		if (vm_fault_quick_hold_pages(&curproc->p_vmspace->vm_map,
-		    exec[i].relocs_ptr, length, VM_PROT_READ | VM_PROT_WRITE,
-		    ma, page_count) == -1) {
+		(*maplen)[i] = vm_fault_quick_hold_pages(
+		    &curproc->p_vmspace->vm_map, exec[i].relocs_ptr, length,
+		    VM_PROT_READ | VM_PROT_WRITE, ma, page_count);
+		if ((*maplen)[i] == -1) {
 			free(ma, DRM_I915_GEM);
 			(*map)[i] = NULL;
 			return (-EFAULT);
@@ -1123,6 +1126,7 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	struct drm_clip_rect *cliprects = NULL;
 	struct intel_ring_buffer *ring;
 	vm_page_t **relocs_ma;
+	int *relocs_len;
 	u32 ctx_id = i915_execbuffer2_get_context_id(*args);
 	u32 exec_start, exec_len;
 	u32 seqno;
@@ -1137,7 +1141,8 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 	if (args->batch_len == 0)
 		return (0);
 
-	ret = validate_exec_list(exec, args->buffer_count, &relocs_ma);
+	ret = validate_exec_list(exec, args->buffer_count, &relocs_ma,
+	    &relocs_len);
 	if (ret != 0)
 		goto pre_struct_lock_err;
 
@@ -1411,13 +1416,11 @@ err:
 pre_struct_lock_err:
 	for (i = 0; i < args->buffer_count; i++) {
 		if (relocs_ma[i] != NULL) {
-			vm_page_unhold_pages(relocs_ma[i], howmany(
-			    exec[i].relocation_count *
-			    sizeof(struct drm_i915_gem_relocation_entry),
-			    PAGE_SIZE));
+			vm_page_unhold_pages(relocs_ma[i], relocs_len[i]);
 			free(relocs_ma[i], DRM_I915_GEM);
 		}
 	}
+	free(relocs_len, DRM_I915_GEM);
 	free(relocs_ma, DRM_I915_GEM);
 	free(cliprects, DRM_I915_GEM);
 	return ret;