Hi
Am 09.01.25 um 17:05 schrieb Matthew Auld:
On 09/01/2025 14:57, Thomas Zimmermann wrote:
Call drm_mode_size_dumb() to compute dumb-buffer scanline pitch
and buffer size. Align the pitch to a multiple of 8. Align the
buffer size according to hardware requirements.
Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
Cc: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
Cc: "Thomas Hellström" <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
---
drivers/gpu/drm/xe/xe_bo.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
index e6c896ad5602..d75e3c39ab14 100644
--- a/drivers/gpu/drm/xe/xe_bo.c
+++ b/drivers/gpu/drm/xe/xe_bo.c
@@ -8,6 +8,7 @@
#include <linux/dma-buf.h>
#include <drm/drm_drv.h>
+#include <drm/drm_dumb_buffers.h>
#include <drm/drm_gem_ttm_helper.h>
#include <drm/drm_managed.h>
#include <drm/ttm/ttm_device.h>
@@ -2535,14 +2536,13 @@ int xe_bo_dumb_create(struct drm_file
*file_priv,
struct xe_device *xe = to_xe_device(dev);
struct xe_bo *bo;
uint32_t handle;
- int cpp = DIV_ROUND_UP(args->bpp, 8);
int err;
u32 page_size = max_t(u32, PAGE_SIZE,
xe->info.vram_flags & XE_VRAM_FLAGS_NEED64K ? SZ_64K : SZ_4K);
- args->pitch = ALIGN(args->width * cpp, 64);
- args->size = ALIGN(mul_u32_u32(args->pitch, args->height),
- page_size);
+ err = drm_mode_size_dumb(dev, args, SZ_64, page_size);
AFAICT this looks to change the behaviour, where u64 size was
technically possible and was allowed given that args->size is u64, but
this helper is limiting the size to u32. Is that intentional? If so,
we should probably make that clear in the commit message.
That's an interesting observation; thanks. The ioctl's internal checks
have always limited the size to 32 bit. [1] I think it is not supposed
to be larger than that. We can change the helper to support 64-bit sizes
as well.
Having said that, is there any use case? Dumb buffers are for software
rendering only. Allocating more than a few dozen MiB seems like a
mistake. Maybe we should rather limit the allowed allocation size instead?
Best regards
Thomas
[1]
https://elixir.bootlin.com/linux/v6.12.6/source/drivers/gpu/drm/drm_dumb_buffers.c#L82
+ if (err)
+ return err;
bo = xe_bo_create_user(xe, NULL, NULL, args->size,
DRM_XE_GEM_CPU_CACHING_WC,
--
--
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)
