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vhost-user: add protocol feature negotiation

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Support a separate bitmask for vhost-user protocol features,
and messages to get/set protocol features.

Invoke them at init.

No features are defined yet.

[ leverage vhost_user_call for request handling -- Yuanhan Liu ]

Signed-off-by: Michael S. Tsirkin <address@hidden>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Tested-by: Marcel Apfelbaum <marcel@redhat.com>
This commit is contained in:
Michael S. Tsirkin 2015-09-23 12:19:56 +08:00
parent 7305483a3d
commit dcb10c000c
4 changed files with 71 additions and 0 deletions
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37
docs/specs/vhost-user.txt
View file

@ -113,6 +113,7 @@ message replies. Most of the requests don't require replies. Here is a list of
the ones that do:
* VHOST_GET_FEATURES
* VHOST_GET_PROTOCOL_FEATURES
* VHOST_GET_VRING_BASE
There are several messages that the master sends with file descriptors passed
@ -127,6 +128,13 @@ in the ancillary data:
If Master is unable to send the full message or receives a wrong reply it will
close the connection. An optional reconnection mechanism can be implemented.
Any protocol extensions are gated by protocol feature bits,
which allows full backwards compatibility on both master
and slave.
As older slaves don't support negotiating protocol features,
a feature bit was dedicated for this purpose:
#define VHOST_USER_F_PROTOCOL_FEATURES 30
Message types
-------------
@ -138,6 +146,8 @@ Message types
Slave payload: u64
Get from the underlying vhost implementation the features bitmask.
Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
* VHOST_USER_SET_FEATURES
@ -146,6 +156,33 @@ Message types
Master payload: u64
Enable features in the underlying vhost implementation using a bitmask.
Feature bit VHOST_USER_F_PROTOCOL_FEATURES signals slave support for
VHOST_USER_GET_PROTOCOL_FEATURES and VHOST_USER_SET_PROTOCOL_FEATURES.
* VHOST_USER_GET_PROTOCOL_FEATURES
Id: 15
Equivalent ioctl: VHOST_GET_FEATURES
Master payload: N/A
Slave payload: u64
Get the protocol feature bitmask from the underlying vhost implementation.
Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
VHOST_USER_GET_FEATURES.
Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
this message even before VHOST_USER_SET_FEATURES was called.
* VHOST_USER_SET_PROTOCOL_FEATURES
Id: 16
Ioctl: VHOST_SET_FEATURES
Master payload: u64
Enable protocol features in the underlying vhost implementation.
Only legal if feature bit VHOST_USER_F_PROTOCOL_FEATURES is present in
VHOST_USER_GET_FEATURES.
Note: slave that reported VHOST_USER_F_PROTOCOL_FEATURES must support
this message even before VHOST_USER_SET_FEATURES was called.
* VHOST_USER_SET_OWNER