From 2c0ec7d7065b4249cf6fa53420458aa9da604338 Mon Sep 17 00:00:00 2001 From: "Michael S. Tsirkin" Date: Fri, 9 Mar 2018 23:23:30 +0200 Subject: content: move 1.0 queue format out to a separate section Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck Approved-by: https://www.oasis-open.org/apps/org/workgroup/virtio/ballot.php?id=3177 Fixes: https://github.com/oasis-tcs/virtio-spec/issues/3 --- content.tex | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-) diff --git a/content.tex b/content.tex index fc1a825..36d54a1 100644 --- a/content.tex +++ b/content.tex @@ -230,7 +230,30 @@ result. The mechanism for bulk data transport on virtio devices is pretentiously called a virtqueue. Each device can have zero or more virtqueues\footnote{For example, the simplest network device has one virtqueue for -transmit and one for receive.}. Each queue has a 16-bit queue size +transmit and one for receive.}. + +Driver makes requests available to device by adding +an available buffer to the queue - i.e. adding a buffer +describing the request to a virtqueue, and optionally triggering +a driver event - i.e. sending a notification to the device. + +Device executes the requests and - when complete - adds +a used buffer to the queue - i.e. lets the driver +know by marking the buffer as used. Device can then trigger +a device event - i.e. send an interrupt to the driver. + +For queue operation detail, see \ref{sec:Basic Facilities of a Virtio Device / Split Virtqueues}~\nameref{sec:Basic Facilities of a Virtio Device / Split Virtqueues}. + +\section{Split Virtqueues}\label{sec:Basic Facilities of a Virtio Device / Split Virtqueues} +The split virtqueue format is the original format used by legacy +virtio devices. The split virtqueue format separates the +virtqueue into several parts, where each part is write-able by +either the driver or the device, but not both. Multiple +locations need to be updated when making a buffer available +and when marking it as used. + + +Each queue has a 16-bit queue size parameter, which sets the number of entries and implies the total size of the queue. -- cgit v1.2.3