From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: 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 51F689864EE for ; Tue, 14 Jun 2022 11:57:44 +0000 (UTC) Date: Tue, 14 Jun 2022 13:57:34 +0200 From: Halil Pasic Message-ID: <20220614135734.534dbc0b.pasic@linux.ibm.com> In-Reply-To: <20220613104038.22010-1-lauralg@amazon.com> References: <20220613104038.22010-1-lauralg@amazon.com> MIME-Version: 1.0 Subject: Re: [virtio-comment] [PATCH v4] virtio-vsock: add max payload size config field Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable To: Laura Loghin Cc: virtio-comment@lists.oasis-open.org, Halil Pasic , Cornelia Huck , "Michael S . Tsirkin" , Stefano Garzarella List-ID: On Mon, 13 Jun 2022 13:40:38 +0300 Laura Loghin wrote: > @@ -57,6 +62,25 @@ \subsection{Device configuration layout}\label{sec:Dev= ice Types / Socket Device > \hline > \end{tabular} > =20 > +The following driver-read-only field, \field{data_max_size} only exists = if > +VIRTIO_VSOCK_F_SIZE_MAX is set. This field specifies the maximum packet = payload > +size for the driver to use. > + > +\devicenormative{\subsubsection}{Device configuration layout}{Device Typ= es / Socket Device / Device configuration layout} > + > +The device MUST NOT change the value exposed through \field{data_max_siz= e}. > + > +\drivernormative{\subsubsection}{Device configuration layout}{Device Typ= es / Socket Device / Device configuration layout} > + > +A driver SHOULD negotiate VIRTIO_VSOCK_F_SIZE_MAX if the device offers i= t. > + > +If the driver negotiates VIRTIO_VSOCK_F_SIZE_MAX, the receive buffers it > +supplies for a packet MUST have a total size that doesn't exceed the siz= e > +\field{data_max_size} (plus header length). > + > +If the driver negotiates VIRTIO_VSOCK_F_SIZE_MAX, it MUST NOT transmit = packets > +of size exceeding the value of \field{data_max_size} (plus header length= ). > + Hi and sorry for being late to the party! I believe I do understand why do we want to put a restriction on the size of the transmitted packets, but I would appreciate if you could explain to me why do we want to limit the receive buffer size. Also I find the wording regarding a little bit ambiguous because in a networking context it also makes sense to talk about the size of the receive buffer. I guess hear we are talking about a single virtio buffer (a descriptor chain described potentially non-continuous (or compact in the mathematical sense of the word) which is composed from as many continuous chunks of memory as many descriptors are contained within the descriptor chain). If we are indeed talking about a single virtio buffer, I don't understand the plural. If not, I'm not sure what are we talking about. Also, do we have some sort of packets may not cross virtio buffer boundaries, or even a single packet per single viritio buffer rule for vsock. I did a quick search and could not find any. Did I overlook something? Should we spell this out? @Michael, Conny: What do you think?=20 Regards, Halil 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-lis= ts Committee: https://www.oasis-open.org/committees/virtio/ Join OASIS: https://www.oasis-open.org/join/