From 0647098d2ed69171b8bdce495cfdd1c5223010f1 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Mon, 21 Mar 2022 15:30:29 +0000 Subject: docs: vhost-user: rewrite section on ring state machine This section is using the word "back-end" to refer to the "slave's back-end", and talking about the "client" for what the rest of the document calls the "slave". Rework it to free the use of the term "back-end", which in the next patch will replace "slave". Signed-off-by: Paolo Bonzini Message-Id: <20210226143413.188046-3-pbonzini@redhat.com> Message-Id: <20220321153037.3622127-6-alex.bennee@linaro.org> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- docs/interop/vhost-user.rst | 46 +++++++++++++++++++++------------------------ 1 file changed, 21 insertions(+), 25 deletions(-) (limited to 'docs') diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst index 1039e7a..1151326 100644 --- a/docs/interop/vhost-user.rst +++ b/docs/interop/vhost-user.rst @@ -332,40 +332,36 @@ bit was dedicated for this purpose:: #define VHOST_USER_F_PROTOCOL_FEATURES 30 -Starting and stopping rings ---------------------------- +Ring states +----------- -Client must only process each ring when it is started. +Rings can be in one of three states: -Client must only pass data between the ring and the backend, when the -ring is enabled. +* stopped: the slave must not process the ring at all. -If ring is started but disabled, client must process the ring without -talking to the backend. +* started but disabled: the slave must process the ring without + causing any side effects. For example, for a networking device, + in the disabled state the slave must not supply any new RX packets, + but must process and discard any TX packets. -For example, for a networking device, in the disabled state client -must not supply any new RX packets, but must process and discard any -TX packets. +* started and enabled. -If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the -ring is initialized in an enabled state. +Each ring is initialized in a stopped state. The slave must start +ring upon receiving a kick (that is, detecting that file descriptor is +readable) on the descriptor specified by ``VHOST_USER_SET_VRING_KICK`` +or receiving the in-band message ``VHOST_USER_VRING_KICK`` if negotiated, +and stop ring upon receiving ``VHOST_USER_GET_VRING_BASE``. -If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is -initialized in a disabled state. Client must not pass data to/from the -backend until ring is enabled by ``VHOST_USER_SET_VRING_ENABLE`` with -parameter 1, or after it has been disabled by -``VHOST_USER_SET_VRING_ENABLE`` with parameter 0. +Rings can be enabled or disabled by ``VHOST_USER_SET_VRING_ENABLE``. -Each ring is initialized in a stopped state, client must not process -it until ring is started, or after it has been stopped. +If ``VHOST_USER_F_PROTOCOL_FEATURES`` has not been negotiated, the +ring starts directly in the enabled state. -Client must start ring upon receiving a kick (that is, detecting that -file descriptor is readable) on the descriptor specified by -``VHOST_USER_SET_VRING_KICK`` or receiving the in-band message -``VHOST_USER_VRING_KICK`` if negotiated, and stop ring upon receiving -``VHOST_USER_GET_VRING_BASE``. +If ``VHOST_USER_F_PROTOCOL_FEATURES`` has been negotiated, the ring is +initialized in a disabled state and is enabled by +``VHOST_USER_SET_VRING_ENABLE`` with parameter 1. -While processing the rings (whether they are enabled or not), client +While processing the rings (whether they are enabled or not), the slave must support changing some configuration aspects on the fly. Multiple queue support -- cgit v1.1