linux-kernel - Re: [PATCH v1] drm/virtio: Extend blob UAPI with deferred-mapping hinting

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Message-ID: <04bb775b-9071-4bef-afaf-a0157bbce2fe@collabora.com>
Date: Fri, 14 Feb 2025 21:55:13 +0300
From: Dmitry Osipenko <dmitry.osipenko@...labora.com>
To: Rob Clark <robdclark@...il.com>
Cc: David Airlie <airlied@...hat.com>, Gerd Hoffmann <kraxel@...hat.com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>,
 Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
 Asahi Lina <lina@...hilina.net>, Alyssa Rosenzweig <alyssa@...enzweig.io>,
 dri-devel@...ts.freedesktop.org, virtualization@...ts.linux.dev,
 linux-kernel@...r.kernel.org, kernel@...labora.com
Subject: Re: [PATCH v1] drm/virtio: Extend blob UAPI with deferred-mapping
 hinting

On 2/14/25 20:45, Rob Clark wrote:
> On Sun, Jan 26, 2025 at 12:43 PM Dmitry Osipenko
> <dmitry.osipenko@...labora.com> wrote:
>>
>> If userspace never maps GEM object, then BO wastes hostmem space
>> because VirtIO-GPU driver maps VRAM BO at the BO's creating time.
>>
>> Make mappings on-demand by adding new RESOURCE_CREATE_BLOB IOCTL/UAPI
>> hinting flag telling that host mapping should be deferred until first
>> mapping is made when the flag is set by userspace.
>>
>> Signed-off-by: Dmitry Osipenko <dmitry.osipenko@...labora.com>
> 
> I suppose we could have just added a new blob_flag, but then userspace
> would need to probe the kernel to see whether the new flag was
> supported.  (Which isn't a big deal, that sort of thing is done in
> many places.)  But extending the struct does make it more transparent
> to userspace.  Either way,
> 
> Reviewed-by: Rob Clark <robdclark@...il.com

Thanks for the review!

-- 
Best regards,
Dmitry