On 2/28/20 10:49 AM, Gerd Hoffmann wrote:
Hi,
Not clue about the others (lima, tiny, panfrost, v3d). Maybe they use
write-combine just because this is what they got by default from
drm_gem_mmap_obj(). Maybe they actually need that. Trying to Cc:
maintainters (and drop stable@).
virtio-gpu needs it, otherwise the host can't show the virtual display.
cirrus bounces everything via blits to vram, so it should be ok without
decrypted. I guess that implies we should make decrypted configurable.
Decrypted here is clearly incorrect and violates the SEV spec, regardless of
a config option.
The only correct way is currently to use dma_alloc_coherent() and
mmap_coherent() to allocate decrypted memory and then use the
pgprot_decrypted flag.
Hmm, virtio-gpu uses the dma api to allow the host access the gem
object. So I think I have to correct the statement above, if I
understands things correctly the dma api will use (properly allocated)
decrypted bounce buffers and the virtio-gpu shmem objects don't need
pgprot_decrypted mappings.
Yes, that sounds more correct. I wonder whether the "pgprot_decrypted()"
perhaps remains from mapping VRAM gem buffers...
/Thomas
That leaves the question what to do about pgprot_writecombine(). Any
comments from the driver maintainers (see first paragraph)?
cheers,
Gerd
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