Re: [report] DMA-API: platform vgem: mapping sg segment longer than device claims to support [len=1048576] [max=65536]
From: Thomas Zimmermann
Date: Fri Jun 20 2025 - 01:17:29 EST
Hi
Am 19.06.25 um 18:07 schrieb Zenghui Yu:
Hi Thomas,
On 2025/6/19 00:25, Thomas Zimmermann wrote:
Hi
Am 18.06.25 um 18:03 schrieb Zenghui Yu:
Hi all,
Running the dmabuf-heap test [*] on mainline kernel triggers the
following splat:
------------[ cut here ]------------
DMA-API: platform vgem: mapping sg segment longer than device claims to support [len=1048576] [max=65536]
Thanks for the bug report. We have a possible fix in the latest drm-
misc-next tree. Does it work if use replace DRM_GEM_SHMEM_DRIVER_OPS
with DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT at [1]?
[1] https://elixir.bootlin.com/linux/v6.16-rc2/source/drivers/gpu/drm/vgem/vgem_drv.c#L118
Thanks for the heads up! So I applied commit 660cd44659a0
("drm/shmem-helper: Import dmabuf without mapping its sg_table") [*] in
my local tree, together with your suggestion:
diff --git a/drivers/gpu/drm/vgem/vgem_drv.c
b/drivers/gpu/drm/vgem/vgem_drv.c
index 2752ab4f1c97..ba0d4e611bd2 100644
--- a/drivers/gpu/drm/vgem/vgem_drv.c
+++ b/drivers/gpu/drm/vgem/vgem_drv.c
@@ -115,7 +115,7 @@ static const struct drm_driver vgem_driver = {
.num_ioctls = ARRAY_SIZE(vgem_ioctls),
.fops = &vgem_driver_fops,
- DRM_GEM_SHMEM_DRIVER_OPS,
+ DRM_GEM_SHMEM_DRIVER_OPS_NO_MAP_SGT,
.gem_create_object = vgem_gem_create_object,
.name = DRIVER_NAME,
The warning message disappeared with that. Thanks again!
Thanks for testing. I'll attempt to get this change into upstream in the
near future.
Best regards
Thomas
[*]
https://gitlab.freedesktop.org/drm/kernel/-/commit/660cd44659a05c5fbfce6d2bb1ce448aa0f35594
Zenghui
--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)