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Re: [PATCH v2 4/4] virtio-gpu: Don't require udmabuf when blob support i
From: |
Gerd Hoffmann |
Subject: |
Re: [PATCH v2 4/4] virtio-gpu: Don't require udmabuf when blob support is enabled |
Date: |
Tue, 27 Sep 2022 10:32:25 +0200 |
On Mon, Sep 26, 2022 at 09:32:40PM +0300, Dmitry Osipenko wrote:
> On 9/23/22 15:32, Gerd Hoffmann wrote:
> > On Tue, Sep 13, 2022 at 12:50:22PM +0200, Antonio Caggiano wrote:
> >> From: Dmitry Osipenko <dmitry.osipenko@collabora.com>
> >>
> >> Host blobs don't need udmabuf, it's only needed by guest blobs. The host
> >> blobs are utilized by the Mesa virgl driver when persistent memory mapping
> >> is needed by a GL buffer, otherwise virgl driver doesn't use blobs.
> >> Persistent mapping support bumps GL version from 4.3 to 4.5 in guest.
> >> Relax the udmabuf requirement.
> >
> > What about blob=on,virgl=off?
> >
> > In that case qemu manages the resources and continued to require
> > udmabuf.
>
> The udmabuf is used only by the blob resource-creation command in Qemu.
> I couldn't find when we could hit that udmabuf code path in Qemu because
> BLOB_MEM_GUEST resource type is used only by crosvm+Venus when crosvm
> uses a dedicated render-server for virglrenderer.
Recent enough linux guest driver will use BLOB_MEM_GUEST resources
with blob=on + virgl=off
> - /dev/udmabuf isn't accessible by normal user
> - udmabuf driver isn't shipped by all of the popular Linux distros,
> for example Debian doesn't ship it
That's why blob resources are off by default.
> Because of all of the above, I don't think it makes sense to
> hard-require udmabuf at the start of Qemu. It's much better to fail
> resource creation dynamically.
Disagree. When virgl/venus is enabled, then yes, qemu would let
virglrenderer manage resources and I'm ok with whatever requirements
virglrenderer has. When qemu manages resources by itself udmabuf is
a hard requirement for blob support though.
take care,
Gerd
[PATCH v2 2/4] virtio-gpu: hostmem, Antonio Caggiano, 2022/09/13
[PATCH v2 1/4] virtio: Add shared memory capability, Antonio Caggiano, 2022/09/13
[PATCH v2 3/4] virtio-gpu: Handle resource blob commands, Antonio Caggiano, 2022/09/13