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Re: [PATCH v2 4/4] virtio-gpu: Don't require udmabuf when blob support i
From: |
Dmitry Osipenko |
Subject: |
Re: [PATCH v2 4/4] virtio-gpu: Don't require udmabuf when blob support is enabled |
Date: |
Tue, 27 Sep 2022 13:44:45 +0300 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 |
On 9/27/22 11:32, Gerd Hoffmann wrote:
> 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
I reproduced this case today using "-device
virtio-gpu-device,blob=true". You're right, it doesn't work without udmabuf.
[ 8.369306] virtio_gpu_dequeue_ctrl_func: 90 callbacks suppressed
[ 8.369311] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1200 (command 0x105)
[ 8.371848] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1205 (command 0x104)
[ 8.373085] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1200 (command 0x105)
[ 8.376273] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1205 (command 0x104)
[ 8.416972] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1200 (command 0x105)
[ 8.418841] [drm:virtio_gpu_dequeue_ctrl_func] *ERROR* response
0x1205 (command 0x104)
I see now why you're wanting to keep the udmabuf requirement for
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.
Let's try to relax the udmabuf requirement only for blob=on,virgl=on.
I'll update this patch.
Thank you very much for the review!
--
Best regards,
Dmitry
[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