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Date:   Thu, 4 Jul 2019 13:10:43 +0200
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 v6 06/18] drm/virtio: remove ttm calls from in
 virtio_gpu_object_{reserve,unreserve}
Message-ID: <20190704111043.5ubc2yjrjphj2iec@sirius.home.kraxel.org>
References: <20190702141903.1131-1-kraxel@redhat.com>
 <20190702141903.1131-7-kraxel@redhat.com>
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  Hi,

> > -       r = ttm_bo_reserve(&bo->tbo, true, false, NULL);
> > +       r = reservation_object_lock_interruptible(bo->gem_base.resv, NULL);
> Can you elaborate a bit about how TTM keeps the BOs alive in, for
> example, virtio_gpu_transfer_from_host_ioctl?  In that function, only
> three TTM functions are called: ttm_bo_reserve, ttm_bo_validate, and
> ttm_bo_unreserve.  I am curious how they keep the BO alive.

It can't go away between reserve and unreserve, and I think it also
can't be evicted then.  Havn't checked how ttm implements that.

cheers,
  Gerd