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Message-ID: <d2c64d09-c4bb-9aed-069d-a9b4d07a1f66@collabora.com>
Date:   Tue, 5 Jul 2022 17:27:35 +0300
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Subject: Re: [PATCH v7 7/9] drm/virtio: Improve DMA API usage for shmem BOs
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To:     Gerd Hoffmann <kraxel@redhat.com>
Cc:     David Airlie <airlied@linux.ie>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        Chia-I Wu <olvaffe@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Emil Velikov <emil.l.velikov@gmail.com>,
        Robin Murphy <robin.murphy@arm.com>,
        =?UTF-8?Q?Thomas_Hellstr=c3=b6m?= <thomas_os@shipmail.org>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        virtualization@lists.linux-foundation.org,
        Dmitry Osipenko <digetx@gmail.com>, kernel@collabora.com
References: <20220630200726.1884320-1-dmitry.osipenko@collabora.com>
 <20220630200726.1884320-8-dmitry.osipenko@collabora.com>
 <20220705135323.emr4gdbcxoisdcxe@sirius.home.kraxel.org>
From:   Dmitry Osipenko <dmitry.osipenko@collabora.com>
In-Reply-To: <20220705135323.emr4gdbcxoisdcxe@sirius.home.kraxel.org>
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Precedence: bulk

Hello Gerd,

On 7/5/22 16:53, Gerd Hoffmann wrote:
>   Hi,
> 
>> -	 * So for the moment keep things as-is, with a bulky comment
>> -	 * for the next person who feels like removing this
>> -	 * drm_dev_set_unique() quirk.
> 
> Dragons lurking here.  It's not the first attempt to ditch this, and so
> far all have been rolled back due to regressions.  Specifically Xorg is
> notoriously picky if it doesn't find its expectations fulfilled.

I saw the previous attempt. Back then it was a mechanically created
patch that didn't get any testing.

> 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.

> What kind of testing has this patch seen?

The Xorg and virgl work perfectly fine in Qemu (with and without IOMMU
enabled in Qemu) and in crosvm (ChromeOS virtual machine).

-- 
Best regards,
Dmitry