diff options
| author | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-04-29 11:09:04 +0000 |
|---|---|---|
| committer | mstsirkin <mstsirkin@0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652> | 2015-04-29 11:09:04 +0000 |
| commit | 3b676c2fb1c342ab01565ab61354b62105640427 (patch) | |
| tree | fee6005c8855b388febbf8f7d9c6b4fc319f0413 | |
| parent | 12e4378536ea473f578edf05b83c78b9f846d516 (diff) | |
VIRTIO-134: Spell out details of indirect elements in chains
1) It's implied that a chain terminates with an indirect descriptor (since
VIRTIO-15) but we didn't spell out that a device MUST NOT continue it.
2) We allow [direct]->[direct]->[indirect], and qemu and bhyve both accept
it. Make it clear that this is valid, thus devices MUST handle it.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
git-svn-id: https://tools.oasis-open.org/version-control/svn/virtio/branches/v1.0@521 0c8fb4dd-22a2-4bb5-bc14-6c75a5f43652
| -rw-r--r-- | content.tex | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/content.tex b/content.tex index 748c78d..2d032a7 100644 --- a/content.tex +++ b/content.tex @@ -477,9 +477,21 @@ one table per descriptor). A driver MUST NOT create a descriptor chain longer than the Queue Size of the device. +A driver MUST NOT set both VIRTQ_DESC_F_INDIRECT and VIRTQ_DESC_F_NEXT +in \field{flags}. + \devicenormative{\paragraph}{Indirect Descriptors}{Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Descriptor Table / Indirect Descriptors} The device MUST ignore the write-only flag (\field{flags}\&VIRTQ_DESC_F_WRITE) in the descriptor that refers to an indirect table. +The device MUST handle the case of zero or more normal chained +descriptors followed by a single descriptor with \field{flags}\&VIRTQ_DESC_F_INDIRECT. + +\begin{note} +While unusual (most implementations either create a chain solely using +non-indirect descriptors, or use a single indirect element), such a +layout is valid. +\end{note} + \subsection{The Virtqueue Available Ring}\label{sec:Basic Facilities of a Virtio Device / Virtqueues / The Virtqueue Available Ring} \begin{lstlisting} |