From: Daniel Vetter <daniel@ffwll.ch>
To: David Stevens <stevensd@chromium.org>
Cc: dri-devel <dri-devel@lists.freedesktop.org>,
virtio-dev@lists.oasis-open.org,
Thomas Zimmermann <tzimmermann@suse.de>,
"Michael S . Tsirkin" <mst@redhat.com>,
David Airlie <airlied@linux.ie>, Jason Wang <jasowang@redhat.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Tomasz Figa <tfiga@chromium.org>,
"moderated list:DMA BUFFER SHARING FRAMEWORK"
<linaro-mm-sig@lists.linaro.org>,
Gerd Hoffmann <kraxel@redhat.com>,
"open list:VIRTIO CORE,
NET..." <virtualization@lists.linux-foundation.org>,
"open list:DMA BUFFER SHARING FRAMEWORK"
<linux-media@vger.kernel.org>
Subject: Re: [PATCH v3 1/4] dma-buf: add support for virtio exported objects
Date: Thu, 14 May 2020 14:30:07 +0200 [thread overview]
Message-ID: <20200514123007.GP206103@phenom.ffwll.local> (raw)
In-Reply-To: <CAD=HUj6k-y1=64zY8ZFOQBZ7WSUWiQfvkiTpXXt10JB_CGqk1A@mail.gmail.com>
On Thu, May 14, 2020 at 05:19:40PM +0900, David Stevens wrote:
> Sorry for the duplicate reply, didn't notice this until now.
>
> > Just storing
> > the uuid should be doable (assuming this doesn't change during the
> > lifetime of the buffer), so no need for a callback.
>
> Directly storing the uuid doesn't work that well because of
> synchronization issues. The uuid needs to be shared between multiple
> virtio devices with independent command streams, so to prevent races
> between importing and exporting, the exporting driver can't share the
> uuid with other drivers until it knows that the device has finished
> registering the uuid. That requires a round trip to and then back from
> the device. Using a callback allows the latency from that round trip
> registration to be hidden.
Uh, that means you actually do something and there's locking involved.
Makes stuff more complicated, invariant attributes are a lot easier
generally. Registering that uuid just always doesn't work, and blocking
when you're exporting?
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
_______________________________________________
dri-devel mailing list
dri-devel@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2020-05-14 12:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-11 11:20 [PATCH v3 0/4] Support virtio cross-device resources David Stevens
2020-03-11 11:20 ` [PATCH v3 1/4] dma-buf: add support for virtio exported objects David Stevens
2020-05-13 15:45 ` Daniel Vetter
2020-05-14 2:08 ` David Stevens
2020-05-14 12:28 ` Daniel Vetter
2020-05-14 7:59 ` Gerd Hoffmann
2020-05-14 12:31 ` Daniel Vetter
2020-05-14 8:19 ` David Stevens
2020-05-14 12:30 ` Daniel Vetter [this message]
2020-05-15 5:07 ` David Stevens
2020-05-15 14:03 ` Daniel Vetter
2020-05-18 11:17 ` Sumit Semwal
2020-03-11 11:20 ` [PATCH v3 2/4] drm/prime: " David Stevens
2020-03-11 11:20 ` [PATCH v3 3/4] virtio-gpu: add VIRTIO_GPU_F_RESOURCE_UUID feature David Stevens
2020-03-11 11:20 ` [PATCH v3 4/4] drm/virtio: Support virtgpu exported resources David Stevens
2020-05-13 16:34 ` Michael S. Tsirkin
2020-05-15 7:26 ` David Stevens
2020-06-08 9:43 ` Michael S. Tsirkin
2020-06-08 10:36 ` David Stevens
2020-06-08 15:17 ` Michael S. Tsirkin
2020-03-20 6:48 ` [PATCH v3 0/4] Support virtio cross-device resources Gerd Hoffmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200514123007.GP206103@phenom.ffwll.local \
--to=daniel@ffwll.ch \
--cc=airlied@linux.ie \
--cc=dri-devel@lists.freedesktop.org \
--cc=jasowang@redhat.com \
--cc=kraxel@redhat.com \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=mst@redhat.com \
--cc=stevensd@chromium.org \
--cc=tfiga@chromium.org \
--cc=tzimmermann@suse.de \
--cc=virtio-dev@lists.oasis-open.org \
--cc=virtualization@lists.linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).