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Date:   Fri, 7 Feb 2020 07:46:30 +0100
From:   Gerd Hoffmann <kraxel@redhat.com>
To:     Chia-I Wu <olvaffe@gmail.com>
Cc:     ML dri-devel <dri-devel@lists.freedesktop.org>,
        Gurchetan Singh <gurchetansingh@chromium.org>,
        David Airlie <airlied@linux.ie>,
        Daniel Vetter <daniel@ffwll.ch>,
        "open list:VIRTIO GPU DRIVER" 
        <virtualization@lists.linux-foundation.org>,
        open list <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] drm/virtio: fix ring free check
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  Hi,

> > +       indirect = virtio_has_feature(vgdev->vdev, VIRTIO_RING_F_INDIRECT_DESC);
> > +       vqcnt = indirect ? 1 : elemcnt;
> Is the feature dynamic and require the lock held?  If not, the result
> can be cached and the fixup can happen before grabbing the lock

Not dynamic, so yes, caching makes sense.

cheers,
  Gerd