From: Keiichi Watanabe <keiichiw@chromium.org> To: Gerd Hoffmann <kraxel@redhat.com> Cc: "Dmitry Sepp" <dmitry.sepp@opensynergy.com>, "Tomasz Figa" <tfiga@chromium.org>, virtio-dev@lists.oasis-open.org, "Linux Media Mailing List" <linux-media@vger.kernel.org>, "Alexandre Courbot" <acourbot@chromium.org>, "Alex Lau" <alexlau@chromium.org>, "Daniel Vetter" <daniel@ffwll.ch>, "Dylan Reid" <dgreid@chromium.org>, "Enrico Granata" <egranata@google.com>, "Frediano Ziglio" <fziglio@redhat.com>, "Hans Verkuil" <hverkuil@xs4all.nl>, "Stéphane Marchesin" <marcheu@chromium.org>, "Pawel Osciak" <posciak@chromium.org>, spice-devel@lists.freedesktop.org, "David Stevens" <stevensd@chromium.org>, uril@redhat.com Subject: Re: [virtio-dev] Re: [PATCH v2 1/1] virtio-video: Add virtio video device specification Date: Wed, 8 Jan 2020 22:52:16 +0900 [thread overview] Message-ID: <CAD90Vcb4Vb49uHGRRg0nJaKo=goH6zOxdQR2d7piLH_byxDYyw@mail.gmail.com> (raw) In-Reply-To: <20191219131234.wm24cazvc7zrnhpn@sirius.home.kraxel.org> Hi Gerd, On Thu, Dec 19, 2019 at 10:12 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > Hi, > > > > However that still doesn't let the driver know which buffers will be > > > dequeued when. A simple example of this scenario is when the guest is > > > done displaying a frame and requeues the buffer back to the decoder. > > > Then the decoder will not choose it for decoding next frames into as > > > long as the frame in that buffer is still used as a reference frame, > > > even if one sends the drain request. > > It might be that I'm getting your point wrong, but do you mean some hardware > > can mark a buffer as ready to be displayed yet still using the underlying > > memory to decode other frames? > > Yes, this is how I understand Tomasz Figa. > > > This means, if you occasionally/intentionally > > write to the buffer you mess up the whole decoding pipeline. > > And to avoid this the buffer handling aspect must be clarified in the > specification. Is the device allowed to continue using the buffer after > finishing decoding and completing the queue request? If so, how do we > hand over buffer ownership back to the driver so it can free the pages? > drain request? How do we handle re-using buffers? Can the driver > simply re-queue them and expect the device figures by itself whenever it > can use the buffer or whenever it is still needed as reference frame? The device shouldn't be able to access buffers after it completes a queue request. The device can touch buffer contents from when a queue request is sent until the device responds it. In contrast, the driver must not modify buffer contents in that period. Regarding re-using, the driver can simply re-queue buffers returned by the device. If the device needs a buffer as reference frame, it must not return the buffer. I'll describe this rule in the next version of the patch. Best regards, Keiichi > > cheers, > Gerd >
WARNING: multiple messages have this Message-ID (diff)
From: Keiichi Watanabe <keiichiw@chromium.org> To: Gerd Hoffmann <kraxel@redhat.com> Cc: "Dmitry Sepp" <dmitry.sepp@opensynergy.com>, "Tomasz Figa" <tfiga@chromium.org>, virtio-dev@lists.oasis-open.org, "Linux Media Mailing List" <linux-media@vger.kernel.org>, "Alexandre Courbot" <acourbot@chromium.org>, "Alex Lau" <alexlau@chromium.org>, "Daniel Vetter" <daniel@ffwll.ch>, "Dylan Reid" <dgreid@chromium.org>, "Enrico Granata" <egranata@google.com>, "Frediano Ziglio" <fziglio@redhat.com>, "Hans Verkuil" <hverkuil@xs4all.nl>, "Stéphane Marchesin" <marcheu@chromium.org>, "Pawel Osciak" <posciak@chromium.org>, spice-devel@lists.freedesktop.org, "David Stevens" <stevensd@chromium.org>, uril@redhat.com Subject: Re: [virtio-dev] Re: [PATCH v2 1/1] virtio-video: Add virtio video device specification Date: Wed, 8 Jan 2020 22:52:16 +0900 [thread overview] Message-ID: <CAD90Vcb4Vb49uHGRRg0nJaKo=goH6zOxdQR2d7piLH_byxDYyw@mail.gmail.com> (raw) In-Reply-To: <20191219131234.wm24cazvc7zrnhpn@sirius.home.kraxel.org> Hi Gerd, On Thu, Dec 19, 2019 at 10:12 PM Gerd Hoffmann <kraxel@redhat.com> wrote: > > Hi, > > > > However that still doesn't let the driver know which buffers will be > > > dequeued when. A simple example of this scenario is when the guest is > > > done displaying a frame and requeues the buffer back to the decoder. > > > Then the decoder will not choose it for decoding next frames into as > > > long as the frame in that buffer is still used as a reference frame, > > > even if one sends the drain request. > > It might be that I'm getting your point wrong, but do you mean some hardware > > can mark a buffer as ready to be displayed yet still using the underlying > > memory to decode other frames? > > Yes, this is how I understand Tomasz Figa. > > > This means, if you occasionally/intentionally > > write to the buffer you mess up the whole decoding pipeline. > > And to avoid this the buffer handling aspect must be clarified in the > specification. Is the device allowed to continue using the buffer after > finishing decoding and completing the queue request? If so, how do we > hand over buffer ownership back to the driver so it can free the pages? > drain request? How do we handle re-using buffers? Can the driver > simply re-queue them and expect the device figures by itself whenever it > can use the buffer or whenever it is still needed as reference frame? The device shouldn't be able to access buffers after it completes a queue request. The device can touch buffer contents from when a queue request is sent until the device responds it. In contrast, the driver must not modify buffer contents in that period. Regarding re-using, the driver can simply re-queue buffers returned by the device. If the device needs a buffer as reference frame, it must not return the buffer. I'll describe this rule in the next version of the patch. Best regards, Keiichi > > cheers, > Gerd > --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org
next prev parent reply other threads:[~2020-01-08 13:52 UTC|newest] Thread overview: 147+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-18 13:02 [PATCH v2 0/1] VirtIO video device specification Keiichi Watanabe 2019-12-18 13:02 ` [virtio-dev] " Keiichi Watanabe 2019-12-18 13:02 ` [PATCH v2 1/1] virtio-video: Add virtio " Keiichi Watanabe 2019-12-18 13:02 ` [virtio-dev] " Keiichi Watanabe 2019-12-18 13:40 ` Gerd Hoffmann 2019-12-18 13:40 ` [virtio-dev] " Gerd Hoffmann 2019-12-18 14:08 ` Tomasz Figa 2019-12-18 14:08 ` Tomasz Figa 2019-12-19 7:46 ` Gerd Hoffmann 2019-12-19 7:46 ` Gerd Hoffmann 2019-12-19 9:48 ` Dmitry Sepp 2019-12-19 9:48 ` Dmitry Sepp 2019-12-19 9:59 ` Tomasz Figa 2019-12-19 9:59 ` Tomasz Figa 2019-12-19 10:54 ` Dmitry Sepp 2019-12-19 10:54 ` Dmitry Sepp 2019-12-19 12:05 ` Tomasz Figa 2019-12-19 12:05 ` Tomasz Figa 2019-12-19 13:12 ` Gerd Hoffmann 2019-12-19 13:12 ` Gerd Hoffmann 2020-01-08 13:52 ` Keiichi Watanabe [this message] 2020-01-08 13:52 ` Keiichi Watanabe 2020-01-09 13:40 ` Gerd Hoffmann 2020-01-09 13:40 ` Gerd Hoffmann 2020-01-09 14:20 ` Tomasz Figa 2020-01-09 14:20 ` Tomasz Figa 2020-01-14 7:18 ` Keiichi Watanabe 2020-01-14 7:18 ` Keiichi Watanabe 2020-01-14 10:35 ` Dmitry Sepp 2020-01-14 10:35 ` Dmitry Sepp 2020-01-15 7:49 ` Keiichi Watanabe 2020-01-15 7:49 ` Keiichi Watanabe 2020-01-15 11:12 ` Tomasz Figa 2020-01-15 11:12 ` Tomasz Figa 2019-12-19 13:01 ` Gerd Hoffmann 2019-12-19 13:01 ` Gerd Hoffmann 2020-01-08 13:50 ` Keiichi Watanabe 2020-01-08 13:50 ` Keiichi Watanabe 2019-12-19 9:26 ` Dmitry Sepp 2019-12-19 9:26 ` [virtio-dev] " Dmitry Sepp 2019-12-19 9:59 ` Tomasz Figa 2019-12-19 9:59 ` [virtio-dev] " Tomasz Figa 2019-12-19 12:54 ` Gerd Hoffmann 2019-12-19 12:54 ` [virtio-dev] " Gerd Hoffmann 2019-12-18 17:29 ` Frediano Ziglio 2019-12-20 14:05 ` Keiichi Watanabe 2019-12-20 14:05 ` [virtio-dev] " Keiichi Watanabe 2019-12-20 15:33 ` Dmitry Sepp 2019-12-20 15:33 ` [virtio-dev] " Dmitry Sepp 2019-12-19 13:28 ` Dmitry Sepp 2019-12-19 13:28 ` [virtio-dev] " Dmitry Sepp 2019-12-20 15:26 ` Keiichi Watanabe 2019-12-20 15:26 ` [virtio-dev] " Keiichi Watanabe 2019-12-20 15:46 ` Dmitry Sepp 2019-12-21 6:46 ` Tomasz Figa 2019-12-21 6:46 ` [virtio-dev] " Tomasz Figa 2019-12-30 12:16 ` Dmitry Sepp 2019-12-30 12:16 ` Dmitry Sepp 2020-01-06 6:31 ` Tomasz Figa 2020-01-06 6:31 ` Tomasz Figa 2020-01-06 8:33 ` Gerd Hoffmann 2020-01-06 8:33 ` Gerd Hoffmann 2020-01-06 9:29 ` Dmitry Sepp 2020-01-06 9:29 ` Dmitry Sepp 2020-01-03 15:47 ` Dmitry Sepp 2020-01-03 15:47 ` [virtio-dev] " Dmitry Sepp 2020-01-06 8:47 ` Gerd Hoffmann 2020-01-06 8:47 ` [virtio-dev] " Gerd Hoffmann 2020-01-06 10:21 ` Keiichi Watanabe 2020-01-06 10:21 ` [virtio-dev] " Keiichi Watanabe 2020-01-06 14:59 ` Dmitry Sepp 2020-01-06 14:59 ` [virtio-dev] " Dmitry Sepp 2020-01-07 13:24 ` Keiichi Watanabe 2020-01-07 13:24 ` [virtio-dev] " Keiichi Watanabe 2020-01-07 16:50 ` Dmitry Sepp 2020-01-07 16:50 ` [virtio-dev] " Dmitry Sepp 2020-01-08 6:59 ` Keiichi Watanabe 2020-01-08 6:59 ` [virtio-dev] " Keiichi Watanabe 2020-01-08 10:00 ` Dmitry Sepp 2020-01-08 10:00 ` [virtio-dev] " Dmitry Sepp 2020-01-08 12:14 ` Keiichi Watanabe 2020-01-08 12:14 ` [virtio-dev] " Keiichi Watanabe 2020-01-08 12:46 ` Tomasz Figa 2020-01-08 12:46 ` [virtio-dev] " Tomasz Figa 2020-01-08 13:05 ` Keiichi Watanabe 2020-01-08 13:05 ` [virtio-dev] " Keiichi Watanabe 2020-01-08 13:11 ` Dmitry Sepp 2020-01-08 13:11 ` [virtio-dev] " Dmitry Sepp 2020-01-08 13:23 ` Keiichi Watanabe 2020-01-08 13:23 ` Keiichi Watanabe 2020-01-08 12:23 ` Keiichi Watanabe 2020-01-08 12:23 ` [virtio-dev] " Keiichi Watanabe 2019-12-20 15:58 ` [PATCH v2 0/1] VirtIO " Dmitry Sepp 2019-12-20 15:58 ` [virtio-dev] " Dmitry Sepp 2019-12-21 4:36 ` Keiichi Watanabe 2019-12-21 4:36 ` [virtio-dev] " Keiichi Watanabe 2019-12-21 6:18 ` Tomasz Figa 2019-12-21 6:18 ` [virtio-dev] " Tomasz Figa 2019-12-21 6:19 ` Tomasz Figa 2019-12-21 6:19 ` [virtio-dev] " Tomasz Figa 2020-01-03 13:05 ` Dmitry Sepp 2020-01-03 13:05 ` [virtio-dev] " Dmitry Sepp 2020-01-06 10:30 ` Keiichi Watanabe 2020-01-06 10:30 ` [virtio-dev] " Keiichi Watanabe 2020-01-06 11:28 ` Dmitry Sepp 2020-01-06 11:28 ` [virtio-dev] " Dmitry Sepp 2020-01-07 10:25 ` Keiichi Watanabe 2020-01-07 10:25 ` [virtio-dev] " Keiichi Watanabe 2020-01-09 14:56 ` Dmitry Sepp 2020-01-09 14:56 ` [virtio-dev] " Dmitry Sepp 2020-01-10 10:16 ` Dmitry Sepp 2020-01-10 10:16 ` Dmitry Sepp 2020-01-10 13:53 ` Keiichi Watanabe 2020-01-10 13:53 ` Keiichi Watanabe 2020-01-10 15:11 ` Dmitry Sepp 2020-01-10 15:11 ` Dmitry Sepp 2020-01-11 16:06 ` Tomasz Figa 2020-01-11 16:06 ` Tomasz Figa 2020-01-13 9:50 ` Dmitry Sepp 2020-01-13 9:50 ` Dmitry Sepp 2020-01-15 11:23 ` Keiichi Watanabe 2020-01-15 11:23 ` Keiichi Watanabe 2020-01-13 9:56 ` Gerd Hoffmann 2020-01-13 9:56 ` Gerd Hoffmann 2020-01-13 10:41 ` Dmitry Sepp 2020-01-13 11:05 ` Gerd Hoffmann 2020-01-13 11:05 ` Gerd Hoffmann 2020-01-13 11:59 ` Tomasz Figa 2020-01-13 11:59 ` Tomasz Figa 2020-01-13 13:26 ` Gerd Hoffmann 2020-01-13 13:26 ` Gerd Hoffmann 2020-01-15 11:00 ` Tomasz Figa 2020-01-15 11:00 ` Tomasz Figa 2020-01-15 11:23 ` Keiichi Watanabe 2020-01-15 11:23 ` Keiichi Watanabe 2020-01-15 11:26 ` Gerd Hoffmann 2020-01-15 11:26 ` Gerd Hoffmann 2020-01-20 7:20 ` Keiichi Watanabe 2020-01-20 7:20 ` Keiichi Watanabe 2020-01-20 10:47 ` Gerd Hoffmann 2020-01-20 10:47 ` Gerd Hoffmann 2020-01-21 2:47 ` Keiichi Watanabe 2020-01-21 2:47 ` Keiichi Watanabe 2020-01-21 6:44 ` Gerd Hoffmann 2020-01-21 6:44 ` Gerd Hoffmann 2020-01-21 8:56 ` Keiichi Watanabe 2020-01-21 8:56 ` Keiichi Watanabe
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