Re: [PATCH v5 0/8] Support virtio-gpu DRM native context

["Alex Bennée" <alex.bennee@linaro.org>]

Dmitry Osipenko <dmitry.osipenko@collabora.com> writes:

> On 1/22/25 20:00, Alex Bennée wrote:
>> Dmitry Osipenko <dmitry.osipenko@collabora.com> writes:
>> 
>>> This patchset adds DRM native context support to VirtIO-GPU on Qemu.
>>>
>>> Contarary to Virgl and Venus contexts that mediates high level GFX APIs,
>>> DRM native context [1] mediates lower level kernel driver UAPI, which
>>> reflects in a less CPU overhead and less/simpler code needed to support it.
>>> DRM context consists of a host and guest parts that have to be implemented
>>> for each GPU driver. On a guest side, DRM context presents a virtual GPU as
>>> a real/native host GPU device for GL/VK applications.
>>>
>>> [1] https://www.youtube.com/watch?v=9sFP_yddLLQ
>>>
>>> Today there are four known DRM native context drivers existing in a wild:
>>>
>>>   - Freedreno (Qualcomm SoC GPUs), completely upstreamed
>>>   - AMDGPU, mostly merged into upstreams
>> 
>> I tried my AMD system today with:
>> 
>> Host:
>>   Aarch64 AVA system
>>   Trixie
>>   virglrenderer @ v1.1.0/99557f5aa130930d11f04ffeb07f3a9aa5963182
>>   -display sdl,gl=on (gtk,gl=on also came up but handled window resizing
>>   poorly)
>>   
>> KVM Guest
>> 
>>   Aarch64
>>   Trixie
>>   mesa @ main/d27748a76f7dd9236bfcf9ef172dc13b8c0e170f
>>   -Dvulkan-drivers=virtio,amd -Dgallium-drivers=virgl,radeonsi -Damdgpu-virtio=true
>> 
>> However when I ran vulkan-info --summary KVM faulted with:
>> 
>>   debian-trixie login: error: kvm run failed Bad address
>>    PC=0000ffffb9aa1eb0 X00=0000ffffba0450a4 X01=0000aaaaf7f32400
>>   X02=000000000000013c X03=0000ffffba045098 X04=0000aaaaf7f3253c
>>   X05=0000ffffba0451d4 X06=00000000c0016900 X07=000000000000000e
>>   X08=0000000000000014 X09=00000000000000ff X10=0000aaaaf7f32500
>>   X11=0000aaaaf7e4d028 X12=0000aaaaf7edbcb0 X13=0000000000000001
>>   X14=000000000000000c X15=0000000000007718 X16=0000ffffb93601f0
>>   X17=0000ffffb9aa1dc0 X18=00000000000076f0 X19=0000aaaaf7f31330
>>   X20=0000aaaaf7f323f0 X21=0000aaaaf7f235e0 X22=000000000000004c
>>   X23=0000aaaaf7f2b5e0 X24=0000aaaaf7ee0cb0 X25=00000000000000ff
>>   X26=0000000000000076 X27=0000ffffcd2b18a8 X28=0000aaaaf7ee0cb0
>>   X29=0000ffffcd2b0bd0 X30=0000ffffb86c8b98  SP=0000ffffcd2b0bd0
>>   PSTATE=20001000 --C- EL0t
>>   QEMU 9.2.50 monitor - type 'help' for more information
>>   (qemu) quit
>> 
>> Which looks very much like the PFN locking failure. However booting up
>> with venus=on instead works. Could there be any differences in the way
>> device memory is mapped in the two cases?
>
> Memory mapping works exactly the same for nctx and venus. Are you on
> 6.13 host kernel?

Yes - with the Altra PCI workaround patches on both host and guest
kernel.

Is there anyway to trace the sharing of device memory on the host so I
can verify its an attempt at device access? The PC looks like its in
user-space but once this fails the guest is suspended so I can't poke
around in its environment.

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro