[RFC PATCH 2/6] drm/xe: Add "null_sparse" type to VM snap properties

[Matthew Brost <matthew.brost@intel.com>]

Add "null_sparse" type to VM snap properties indicating the VMA reads
zero and writes are droppped. This is useful information for debug and
will help build a robust GPU hang replay tool.

The current format is:

[<vma address>]: <permissions>|<type>

Permissions has two options, either "read_only" or "read_write".

Type has three options, either "userptr", "null_sparse", or "bo".

Cc: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
---
 drivers/gpu/drm/xe/xe_vm.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index 5f9651a4c364..469b00150d87 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -3242,6 +3242,7 @@ struct xe_vm_snapshot {
 		unsigned long len;
 #define XE_VM_SNAP_FLAG_USERPTR		BIT(0)
 #define XE_VM_SNAP_FLAG_READ_ONLY	BIT(1)
+#define XE_VM_SNAP_FLAG_IS_NULL		BIT(2)
 		unsigned long flags;
 		struct xe_bo *bo;
 		void *data;
@@ -3299,6 +3300,8 @@ struct xe_vm_snapshot *xe_vm_snapshot_capture(struct xe_vm *vm)
 
 			snap->snap[i].bo_ofs = xe_vma_userptr(vma);
 			snap->snap[i].flags |= XE_VM_SNAP_FLAG_USERPTR;
+		} else if (xe_vma_is_null(vma)) {
+			snap->snap[i].flags |= XE_VM_SNAP_FLAG_IS_NULL;
 		} else {
 			snap->snap[i].data = ERR_PTR(-ENOENT);
 		}
@@ -3319,7 +3322,8 @@ void xe_vm_snapshot_capture_delayed(struct xe_vm_snapshot *snap)
 		struct xe_bo *bo = snap->snap[i].bo;
 		int err;
 
-		if (IS_ERR(snap->snap[i].data))
+		if (IS_ERR(snap->snap[i].data) ||
+		    snap->snap[i].flags & XE_VM_SNAP_FLAG_IS_NULL)
 			continue;
 
 		snap->snap[i].data = kvmalloc(snap->snap[i].len, GFP_USER);
@@ -3371,6 +3375,8 @@ void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct drm_printer *p)
 		drm_printf(p, "[%llx].properties: %s|%s\n", snap->snap[i].ofs,
 			   snap->snap[i].flags & XE_VM_SNAP_FLAG_READ_ONLY ?
 			   "read_only" : "read_write",
+			   snap->snap[i].flags & XE_VM_SNAP_FLAG_IS_NULL ?
+			   "null_sparse" :
 			   snap->snap[i].flags & XE_VM_SNAP_FLAG_USERPTR ?
 			   "userptr" : "bo");
 
@@ -3380,6 +3386,9 @@ void xe_vm_snapshot_print(struct xe_vm_snapshot *snap, struct drm_printer *p)
 			continue;
 		}
 
+		if (snap->snap[i].flags & XE_VM_SNAP_FLAG_IS_NULL)
+			continue;
+
 		drm_printf(p, "[%llx].data: ", snap->snap[i].ofs);
 
 		for (j = 0; j < snap->snap[i].len; j += sizeof(u32)) {
-- 
2.34.1