Am 16.08.22 um 13:44 schrieb Dmitry Osipenko:
[SNIP]
The other complication I noticed is that we don't seem to keep around
the fd after importing to a GEM handle. And I could imagine that
doing so could cause issues with too many fd's. So I guess the best
thing is to keep the status quo and let drivers that cannot mmap
imported buffers just fail mmap?
That actually should be all the drivers excluding those that use
DRM-SHMEM because only DRM-SHMEM uses dma_buf_mmap(), that's why it
works for Panfrost. I'm pretty sure mmaping of imported GEMs doesn't
work for the MSM driver, isn't it?
Intel and AMD drivers don't allow to map the imported dma-bufs. Both
refuse to do the mapping.
Although, AMDGPU "succeeds" to do the mapping using
AMDGPU_GEM_DOMAIN_GTT, but then touching the mapping causes bus fault,
hence mapping actually fails. I think it might be the AMDGPU
driver/libdrm bug, haven't checked yet.
That's then certainly broken somehow. Amdgpu should nerve ever have
allowed to mmap() imported DMA-bufs and the last time I check it didn't.
Regards,
Christian.
So we're back to the point that neither of DRM drivers need to map
imported dma-bufs and this was never tested. In this case this patch is
valid, IMO.
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