linux-kernel - Re: [PATCH v18 24/26] drm/virtio: Attach shmem BOs dynamically

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Message-ID: <fe7188d5-d70c-0f4a-7998-99f2efcffdb6@collabora.com>
Date:   Thu, 23 Nov 2023 01:37:21 +0300
From:   Dmitry Osipenko <dmitry.osipenko@...labora.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
Cc:     David Airlie <airlied@...il.com>,
        Gerd Hoffmann <kraxel@...hat.com>,
        Gurchetan Singh <gurchetansingh@...omium.org>,
        Chia-I Wu <olvaffe@...il.com>, Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Christian König <christian.koenig@....com>,
        Qiang Yu <yuq825@...il.com>,
        Steven Price <steven.price@....com>,
        Emma Anholt <emma@...olt.net>, Melissa Wen <mwen@...lia.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        kernel@...labora.com, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v18 24/26] drm/virtio: Attach shmem BOs dynamically

On 11/13/23 12:57, Boris Brezillon wrote:
> On Mon, 30 Oct 2023 02:02:03 +0300
> Dmitry Osipenko <dmitry.osipenko@...labora.com> wrote:
> 
>> Prepare for addition of memory shrinker support by attaching shmem pages
>> to host dynamically on first use. Previously the attachment vq command
>> wasn't fenced and there was no vq kick made in the BO creation code path,
>> hence the attachment already was happening dynamically, but implicitly.
>> Making attachment explicitly dynamic will allow to simplify and reuse more
>> code when shrinker will be added. The virtio_gpu_object_shmem_init() now
>> works under the held reservation lock, which will be important to have for
>> shrinker to avoid moving pages while they are in active use by the driver.
> Ah, this commit might actually help getting rid of the workaround
> introduced in "drm/shmem-helper: Add common memory shrinker".

Not really. The virtio_gpu_free_object() is unchanged, it's only
allocation that is being deferred and it's only done for a one BO type
(virtio-gpu has multiple BO types).

-- 
Best regards,
Dmitry