From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-1157-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 2F2C998601F for ; Thu, 26 Mar 2020 11:52:50 +0000 (UTC) Date: Thu, 26 Mar 2020 12:52:36 +0100 From: Cornelia Huck Message-ID: <20200326125236.4bf0c5aa.cohuck@redhat.com> In-Reply-To: <20200326071301-mutt-send-email-mst@kernel.org> References: <20200326104320.24f49d5a.cohuck@redhat.com> <20200326071301-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 Subject: [virtio-comment] Re: [PATCH v7] virtio-net: Add support for the flexible driver notification structure. Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit To: "Michael S. Tsirkin" Cc: Vitaly Mireyno , "virtio-comment@lists.oasis-open.org" , Jason Wang , Ariel Elior List-ID: On Thu, 26 Mar 2020 07:26:16 -0400 "Michael S. Tsirkin" wrote: > On Thu, Mar 26, 2020 at 10:43:20AM +0100, Cornelia Huck wrote: > > On Wed, 18 Mar 2020 18:29:19 +0000 > > Vitaly Mireyno wrote: > > > + > > > +\begin{note} > > > +If \field{notify_off_multiplier} > 0, the virtqueue number can potentially be > > > +derived by the device from the Queue Notify address, so \field{vqn} may be > > > +redundant. > > I feel this is confusing the reader more than it explains. > the field is always there. It's either the virtqueue number or > whatever we get from the device. "the virtqueue number can potentially be derived by the device from the Queue Notify address, so obtaining the virtqueue number from \field{vqn} is not needed" ? > > > > +\end{note} > > > + (...) > > > @@ -4180,6 +4205,33 @@ \subsubsection{Legacy Interface: Framing Requirements}\label{sec:Device > > > See \ref{sec:Basic > > > Facilities of a Virtio Device / Virtqueues / Message Framing}. > > > > > > +\subsubsection{Driver Notifications}\label{sec:Device Types / Network Device / Device Operation / Driver Notifications} > > > +As mentioned in section \ref{sec:Virtqueues / Driver notifications}, when the > > > +driver is required to send an available buffer notification to the device, it > > > +always sends the virtqueue number to be notified. The method of delivering > > > +notifications is transport specific. With the PCI transport, the device can > > > +optionally provide a distinct per-virtqueue address for driver notifications > > > +(Queue Notify address). In this case, the virtqueue number can potentially be > > > +derived by the device from the Queue Notify address. For devices, that provide > > > +per-virtqueue Queue Notify addresses and are able to derive the virtqueue number > > > +from that address, the virtqueue number in the notification data is redundant. > > > > I would keep the remark that the queue number might be redundant with > > the PCI transport. > > I feel redundant is too strong a word. If anything sending data we just > read from device back to it is definitely redundant. > Spec says send it so we send it. > Maybe say it can be ignored by the device? Maybe "not needed"? (see above) > > > > +On the other hand, some devices can benefit from receiving additional data with > > > +driver notifications. An example could be a hardware device implementing multiple > > > +protocols (with virtio being one of them), so the extra notification data could > > > +serve as a notification type indication or a protocol indication. > > > > Hm... what about replacing the whole text above with > > > > "Driver notifications (\ref{sec:Virtqueues / Driver notifications}) > > always contain at least the virtqueue number for which buffers are > > available. Some devices can benefit from receiving additional data with > > driver notifications. For example, a hardware device implementing > > multiple protocols (with virtio being one of them) could benefit from a > > notification type indication or a protocol indication." > > > My problem with both versions is that it talks about > "additional information" while in fact it's information that > comes from the device itself. "per-device information", maybe? This publicly archived list offers a means to provide input to the OASIS Virtual I/O Device (VIRTIO) TC. In order to verify user consent to the Feedback License terms and to minimize spam in the list archive, subscription is required before posting. Subscribe: virtio-comment-subscribe@lists.oasis-open.org Unsubscribe: virtio-comment-unsubscribe@lists.oasis-open.org List help: virtio-comment-help@lists.oasis-open.org List archive: https://lists.oasis-open.org/archives/virtio-comment/ Feedback License: https://www.oasis-open.org/who/ipr/feedback_license.pdf List Guidelines: https://www.oasis-open.org/policies-guidelines/mailing-lists Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/