lkml.org 
[lkml]   [2020]   [Feb]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v5 1/3] drm/shmem: add support for per object caching flags.
  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.

That leaves the question what to do about pgprot_writecombine(). Any
comments from the driver maintainers (see first paragraph)?

cheers,
Gerd

\
 
 \ /
  Last update: 2020-02-28 10:50    [W:0.126 / U:0.056 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site