linux-kernel - Re: [PATCH v7 7/9] drm/virtio: Improve DMA API usage for shmem BOs

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Date:   Wed, 6 Jul 2022 02:08:47 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Gerd Hoffmann <kraxel@...hat.com>, David Airlie <airlied@...ux.ie>,
        Robin Murphy <robin.murphy@....com>,
        Thomas Hellström <thomas_os@...pmail.org>,
        Emil Velikov <emil.l.velikov@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Dmitry Osipenko <digetx@...il.com>, kernel@...labora.com,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH v7 7/9] drm/virtio: Improve DMA API usage for shmem BOs

On 7/6/22 00:39, Rob Clark wrote:
> On Tue, Jul 5, 2022 at 10:02 AM Dmitry Osipenko
> <dmitry.osipenko@...labora.com> wrote:
>>
>> On 7/5/22 18:45, Gerd Hoffmann wrote:
>>>   Hi,
>>>
>>>>> Also note that pci is not the only virtio transport we have.
>>>>
>>>> The VirtIO indeed has other transports, but only PCI is really supported
>>>> in case of the VirtIO-GPU in kernel and in Qemu/crosvm, AFAICT. Hence
>>>> only the PCI transport was tested.
>>>
>>> qemu -M microvm \
>>>   -global virtio-mmio.force-legacy=false \
>>>   -device virtio-gpu-device
>>>
>>> Gives you a functional virtio-gpu device on virtio-mmio.
>>>
>>> aarch64 virt machines support both pci and mmio too.
>>> s390x has virtio-gpu-ccw ...
>>
>> Gerd, thank you very much! It's was indeed unclear to me how to test the
>> MMIO GPU, but yours variant with microvm works! I was looking for trying
>> aarch64 in the past, but it also was unclear how to do it since there is
>> no DT support for the VirtIO-GPU, AFAICS.
> 
> just a drive-by note, IME on aarch64 kernels, at least with crosvm,
> virtgpu is also a pci device.. the non-pci things in the guest kernel
> use dt, but devices on discoverable busses like pci don't need dt
> nodes (which is true also in the non-vm case)

Sure, I was only looking how to test MMIO GPU on aarch64. Since I
haven't a found a way to test MMIO back then, I concluded that the MMIO
case wasn't really well supported.

-- 
Best regards,
Dmitry