[PATCH 2/2] drm/amdgpu/dma_buf: fix page_link check

[Christian König]

Am 07.04.25 um 16:44 schrieb Matthew Auld:
> On 07/04/2025 15:32, Christian König wrote:
>> Am 07.04.25 um 16:18 schrieb Matthew Auld:
>>> The page_link lower bits of the first sg could contain something like
>>> SG_END, if we are mapping a single VRAM page or contiguous blob which
>>> fits into one sg entry. Rather pull out the struct page, and use that in
>>> our check to know if we mapped struct pages vs VRAM.
>>>
>>> Fixes: f44ffd677fb3 ("drm/amdgpu: add support for exporting VRAM using DMA-buf v3")
>>> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
>>> Cc: Christian König <christian.koenig at amd.com>
>>> Cc: amd-gfx at lists.freedesktop.org
>>> Cc: <stable at vger.kernel.org> # v5.8+
>>
>> Good point, haven't thought about that at all since we only abuse the sg table as DMA addr container.
>>
>> Reviewed-by: Christian König <christian.koenig at amd.com>
>>
>> Were is patch #1 from this series?
>
> That one is xe specific:
> https://lore.kernel.org/intel-xe/20250407141823.44504-3-matthew.auld@intel.com/T/#m4ef16e478cfc8853d4518448dd345a66d5a7f6d9
>
> I copied your approach with using page_link here, but with added sg_page().

Feel free to add my Acked-by to that one as well.

I just wanted to double check if we need to push the patches upstream together, but that looks like we can take each through individual branches.

Thanks,
Christian.

>
>>
>> Thanks,
>> Christian.
>>
>>> ---
>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>> index 9f627caedc3f..c9842a0e2a1c 100644
>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
>>> @@ -184,7 +184,7 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
>>>                    struct sg_table *sgt,
>>>                    enum dma_data_direction dir)
>>>   {
>>> -    if (sgt->sgl->page_link) {
>>> +    if (sg_page(sgt->sgl)) {
>>>           dma_unmap_sgtable(attach->dev, sgt, dir, 0);
>>>           sg_free_table(sgt);
>>>           kfree(sgt);
>>
>