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From:   Rob Clark <robdclark@gmail.com>
Date:   Mon, 8 May 2023 06:59:02 -0700
Message-ID: <CAF6AEGs4fuq4i8UJdO5hvgHTNhzFMKGZ87+w1oyvL0LAqWio6A@mail.gmail.com>
Subject: Re: [PATCH v6 0/3] Add sync object UAPI support to VirtIO-GPU driver
To:     Gurchetan Singh <gurchetansingh@chromium.org>
Cc:     Dmitry Osipenko <dmitry.osipenko@collabora.com>,
        Gerd Hoffmann <kraxel@redhat.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        kernel@collabora.com, virtualization@lists.linux-foundation.org,
        David Airlie <airlied@redhat.com>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        =?UTF-8?B?TWFyZWsgT2zFocOhaw==?= <maraeo@gmail.com>,
        Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@amd.com>,
        Emil Velikov <emil.velikov@collabora.com>
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On Wed, May 3, 2023 at 10:07=E2=80=AFAM Gurchetan Singh
<gurchetansingh@chromium.org> wrote:
>
>
>
> On Mon, May 1, 2023 at 8:38=E2=80=AFAM Dmitry Osipenko <dmitry.osipenko@c=
ollabora.com> wrote:
>>
>> On 4/16/23 14:52, Dmitry Osipenko wrote:
>> > We have multiple Vulkan context types that are awaiting for the additi=
on
>> > of the sync object DRM UAPI support to the VirtIO-GPU kernel driver:
>> >
>> >  1. Venus context
>> >  2. Native contexts (virtio-freedreno, virtio-intel, virtio-amdgpu)
>> >
>> > Mesa core supports DRM sync object UAPI, providing Vulkan drivers with=
 a
>> > generic fencing implementation that we want to utilize.
>> >
>> > This patch adds initial sync objects support. It creates fundament for=
 a
>> > further fencing improvements. Later on we will want to extend the Virt=
IO-GPU
>> > fencing API with passing fence IDs to host for waiting, it will be a n=
ew
>> > additional VirtIO-GPU IOCTL and more. Today we have several VirtIO-GPU=
 context
>> > drivers in works that require VirtIO-GPU to support sync objects UAPI.
>> >
>> > The patch is heavily inspired by the sync object UAPI implementation o=
f the
>> > MSM driver.
>>
>> Gerd, do you have any objections to merging this series?
>>
>> We have AMDGPU [1] and Intel [2] native context WIP drivers depending on
>> the sync object support. It is the only part missing from kernel today
>> that is wanted by the native context drivers. Otherwise, there are few
>> other things in Qemu and virglrenderer left to sort out.
>>
>> [1] https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21658
>> [2] https://gitlab.freedesktop.org/digetx/mesa/-/commits/native-context-=
iris
>
>
> I'm not saying this change isn't good, just it's probably possible to imp=
lement the native contexts (even up to even VK1.2) without it.  But this pa=
tch series may be the most ergonomic way to do it, given how Mesa is design=
ed.  But you probably want one of Mesa MRs reviewed first before merging (I=
 added a comment on the amdgpu change) and that is a requirement [a].
>
> [a] "The userspace side must be fully reviewed and tested to the standard=
s of that user space project. For e.g. mesa this means piglit testcases and=
 review on the mailing list. This is again to ensure that the new interface=
 actually gets the job done." -- from the requirements
>

tbh, the syncobj support is all drm core, the only driver specifics is
the ioctl parsing.  IMHO existing tests and the two existing consumers
are sufficient.  (Also, considering that additional non-drm
dependencies involved.)

If this was for the core drm syncobj implementation, and not just
driver ioctl parsing and wiring up the core helpers, I would agree
with you.

BR,
-R