From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-comment-return-846-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 3777C985DC1 for ; Tue, 17 Sep 2019 07:18:16 +0000 (UTC) From: =?UTF-8?q?Eugenio=20P=C3=A9rez?= Date: Tue, 17 Sep 2019 09:18:12 +0200 Message-Id: <20190917071812.529-1-eperezma@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit Subject: [virtio-comment] [PATCH] block: Add multiqueue To: virtio-comment@lists.oasis-open.org List-ID: The spec miss that field. Add the field, some description around. I've followed the network device's multiqueue mentions, and copied / adapted when needed. Signed-off-by: Eugenio Pérez --- content.tex | 24 ++++++++++++++++++++---- 1 file changed, 20 insertions(+), 4 deletions(-) diff --git a/content.tex b/content.tex index 37a2190..85e500b 100644 --- a/content.tex +++ b/content.tex @@ -3822,7 +3822,7 @@ \section{Block Device}\label{sec:Device Types / Block Device} The virtio block device is a simple virtual block device (ie. disk). Read and write requests (and other exotic requests) are -placed in the queue, and serviced (probably out of order) by the +placed in one of its queues, and serviced (probably out of order) by the device except where noted. \subsection{Device ID}\label{sec:Device Types / Block Device / Device ID} @@ -3830,9 +3830,14 @@ \subsection{Device ID}\label{sec:Device Types / Block Device / Device ID} \subsection{Virtqueues}\label{sec:Device Types / Block Device / Virtqueues} \begin{description} -\item[0] requestq +\item[0] requestq1 +\item[\ldots] +\item[N] requestqN \end{description} + N=1 if VIRTIO_BLK_F_MQ is not negotiated, otherwise N is set by + \field{num_queues}. + \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits} \begin{description} @@ -3857,6 +3862,8 @@ \subsection{Feature bits}\label{sec:Device Types / Block Device / Feature bits} \item[VIRTIO_BLK_F_CONFIG_WCE (11)] Device can toggle its cache between writeback and writethrough modes. +\item[VIRTIO_BLK_F_MQ (12)] Device supports multiqueue. + \item[VIRTIO_BLK_F_DISCARD (13)] Device can support discard command, maximum discard sectors size in \field{max_discard_sectors} and maximum discard segment number in \field{max_discard_seg}. @@ -3885,6 +3892,9 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / present. The availability of the others all depend on various feature bits as indicated above. +The field \field{num_queues} only exists if VIRTIO_BLK_F_MQ is set. This field specifies +the number of queues. + The parameters in the configuration space of the device \field{max_discard_sectors} \field{discard_sector_alignment} are expressed in 512-byte units if the VIRTIO_BLK_F_DISCARD feature bit is negotiated. The \field{max_write_zeroes_sectors} @@ -3913,7 +3923,8 @@ \subsection{Device configuration layout}\label{sec:Device Types / Block Device / le32 opt_io_size; } topology; u8 writeback; - u8 unused0[3]; + u8 unused0; + u16 num_queues; le32 max_discard_sectors; le32 max_discard_seg; le32 discard_sector_alignment; @@ -3973,6 +3984,11 @@ \subsection{Device Initialization}\label{sec:Device Types / Block Device / Devic \field{max_write_zeroes_sectors} and \field{max_write_zeroes_seg} can be read to determine the maximum write zeroes sectors and maximum number of write zeroes segments for the block driver to use. + +\item If the VIRTIO_BLK_F_MQ feature is negotiated, \field{num_queues} field + can be read to determine the number of queues. The driver does not use more + queues than guest's number of CPUs. + \end{enumerate} \drivernormative{\subsubsection}{Device Initialization}{Device Types / Block Device / Device Initialization} @@ -4024,7 +4040,7 @@ \subsubsection{Legacy Interface: Device Initialization}\label{sec:Device Types / \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Operation} -The driver queues requests to the virtqueue, and they are used by +The driver queues requests to the virtqueues, and they are used by the device (not necessarily in order). Each request is of form: \begin{lstlisting} -- 2.16.5 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/