diff options
Diffstat (limited to 'docs/specs/vhost-user.txt')
| -rw-r--r-- | docs/specs/vhost-user.txt | 77 |
1 files changed, 75 insertions, 2 deletions
diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt index 650bb18186..4eadad1d6b 100644 --- a/docs/specs/vhost-user.txt +++ b/docs/specs/vhost-user.txt @@ -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 +128,30 @@ 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 + +Multiple queue support +---------------------- + +Multiple queue is treated as a protocol extension, hence the slave has to +implement protocol features first. The multiple queues feature is supported +only when the protocol feature VHOST_USER_PROTOCOL_F_MQ (bit 0) is set: +#define VHOST_USER_PROTOCOL_F_MQ 0 + +The max number of queues the slave supports can be queried with message +VHOST_USER_GET_PROTOCOL_FEATURES. Master should stop when the number of +requested queues is bigger than that. + +As all queues share one connection, the master uses a unique index for each +queue in the sent message to identify a specified queue. One queue pair +is enabled initially. More queues are enabled dynamically, by sending +message VHOST_USER_SET_VRING_ENABLE. + Message types ------------- @@ -138,6 +163,8 @@ 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 +173,33 @@ 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 @@ -157,10 +211,10 @@ Message types as an owner of the session. This can be used on the Slave as a "session start" flag. - * VHOST_USER_RESET_OWNER + * VHOST_USER_RESET_DEVICE Id: 4 - Equivalent ioctl: VHOST_RESET_OWNER + Equivalent ioctl: VHOST_RESET_DEVICE Master payload: N/A Issued when a new connection is about to be closed. The Master will no @@ -264,3 +318,22 @@ Message types Bits (0-7) of the payload contain the vring index. Bit 8 is the invalid FD flag. This flag is set when there is no file descriptor in the ancillary data. + + * VHOST_USER_GET_QUEUE_NUM + + Id: 17 + Equivalent ioctl: N/A + Master payload: N/A + Slave payload: u64 + + Query how many queues the backend supports. This request should be + sent only when VHOST_USER_PROTOCOL_F_MQ is set in quried protocol + features by VHOST_USER_GET_PROTOCOL_FEATURES. + + * VHOST_USER_SET_VRING_ENABLE + + Id: 18 + Equivalent ioctl: N/A + Master payload: vring state description + + Signal slave to enable or disable corresponding vring. |