From: "Thomas Hellström (VMware)" <thomas_os@shipmail.org>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: dri-devel@lists.freedesktop.org, Guillaume.Gardet@arm.com,
David Airlie <airlied@linux.ie>,
open list <linux-kernel@vger.kernel.org>,
gurchetansingh@chromium.org, tzimmermann@suse.de,
yuq825@gmail.com, noralf@tronnes.org, robh@kernel.org
Subject: Re: [PATCH v5 1/3] drm/shmem: add support for per object caching flags.
Date: Fri, 28 Feb 2020 10:54:54 +0100 [thread overview]
Message-ID: <99eea905-db5c-4e07-7b93-6de3482e02f7@shipmail.org> (raw)
In-Reply-To: <20200228094903.g7yf73mtnbjyu4ez@sirius.home.kraxel.org>
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
next prev parent reply other threads:[~2020-02-28 9:55 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200226154752.24328-1-kraxel@redhat.com>
2020-02-26 15:47 ` [PATCH v5 1/3] drm/shmem: add support for per object caching flags Gerd Hoffmann
2020-02-26 16:51 ` Guillaume Gardet
2020-02-26 18:24 ` Thomas Hellström (VMware)
2020-02-27 0:02 ` Chia-I Wu
2020-02-27 7:16 ` Thomas Hellström (VMware)
2020-02-27 7:53 ` Gerd Hoffmann
2020-02-27 8:10 ` Thomas Hellström (VMware)
2020-02-27 10:56 ` Gerd Hoffmann
2020-02-27 12:16 ` Thomas Hellström (VMware)
2020-02-27 13:21 ` Gerd Hoffmann
2020-02-27 13:44 ` Thomas Hellström (VMware)
2020-02-27 13:49 ` Thomas Hellström (VMware)
2020-02-28 9:49 ` Gerd Hoffmann
2020-02-28 9:54 ` Thomas Hellström (VMware) [this message]
2020-02-28 10:46 ` Gerd Hoffmann
2020-03-02 1:56 ` Qiang Yu
2020-02-26 15:47 ` [PATCH v5 2/3] drm/virtio: fix mmap page attributes Gerd Hoffmann
2020-02-26 16:52 ` Guillaume Gardet
2020-02-26 15:47 ` [PATCH v5 3/3] drm/udl: simplify gem object mapping Gerd Hoffmann
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