Re: [Qemu-devel] [RFC 1/2] spec/vhost-user: Introduce secondary channel for slave initiated requests

[Marc-André Lureau]

Hi

On Tue, Apr 11, 2017 at 12:10 PM Maxime Coquelin <address@hidden>
wrote:

> This vhost-user specification update aims at enabling the
> slave to send requests to the master using a dedicated socket
> created by the master.
>
> It can be used for example when the slave implements a device
> IOTLB to send cache miss requests to the master.
>
> The message types list is updated with an "Initiator" field to
> indicate for each type whether the master and/or slave can
> initiate the request.
>
> Signed-off-by: Maxime Coquelin <address@hidden>
>

This is very similar to a patch I proposed for shutdown slave initiated
requests:
https://lists.gnu.org/archive/html/qemu-devel/2016-04/msg00095.html


> ---
>  docs/specs/vhost-user.txt | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/docs/specs/vhost-user.txt b/docs/specs/vhost-user.txt
> index 036890f..b365047 100644
> --- a/docs/specs/vhost-user.txt
> +++ b/docs/specs/vhost-user.txt
> @@ -139,6 +139,7 @@ in the ancillary data:
>   * VHOST_USER_SET_VRING_KICK
>   * VHOST_USER_SET_VRING_CALL
>   * VHOST_USER_SET_VRING_ERR
> + * VHOST_USER_SET_SLAVE_REQ_FD
>
>
I like "slave-req-fd" better than "slave-fd"


>  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.
> @@ -150,6 +151,11 @@ As older slaves don't support negotiating protocol
> features,
>  a feature bit was dedicated for this purpose:
>  #define VHOST_USER_F_PROTOCOL_FEATURES 30
>
> +If the slave supports VHOST_USER_PROTOCOL_F_SLAVE_REQ protocol feature,
> the
> +master may create a secondary Unix domain socket and send its file
> descriptor
> +to the slave using VHOST_USER_SET_SLAVE_REQ_FD request. This new channel
> enables
> +the slave to send message requests and master to send message replies.
> +
>  Starting and stopping rings
>  ----------------------
>  Client must only process each ring when it is started.
> @@ -260,6 +266,7 @@ Protocol features
>  #define VHOST_USER_PROTOCOL_F_RARP           2
>  #define VHOST_USER_PROTOCOL_F_REPLY_ACK      3
>  #define VHOST_USER_PROTOCOL_F_MTU            4
> +#define VHOST_USER_PROTOCOL_F_SLAVE_REQ      5
>
>  Message types
>  -------------
> @@ -268,6 +275,7 @@ Message types
>
>        Id: 1
>        Equivalent ioctl: VHOST_GET_FEATURES
> +      Initiator: Master
>        Master payload: N/A
>        Slave payload: u64
>
> @@ -279,6 +287,7 @@ Message types
>
>        Id: 2
>        Ioctl: VHOST_SET_FEATURES
> +      Initiator: Master
>        Master payload: u64
>
>        Enable features in the underlying vhost implementation using a
> bitmask.
> @@ -289,6 +298,7 @@ Message types
>
>        Id: 15
>        Equivalent ioctl: VHOST_GET_FEATURES
> +      Initiator: Master
>        Master payload: N/A
>        Slave payload: u64
>
> @@ -302,6 +312,7 @@ Message types
>
>        Id: 16
>        Ioctl: VHOST_SET_FEATURES
> +      Initiator: Master
>        Master payload: u64
>
>        Enable protocol features in the underlying vhost implementation.
> @@ -314,6 +325,7 @@ Message types
>
>        Id: 3
>        Equivalent ioctl: VHOST_SET_OWNER
> +      Initiator: Master
>        Master payload: N/A
>
>        Issued when a new connection is established. It sets the current
> Master
> @@ -323,6 +335,7 @@ Message types
>   * VHOST_USER_RESET_OWNER
>
>        Id: 4
> +      Initiator: Master
>        Master payload: N/A
>
>        This is no longer used. Used to be sent to request disabling
> @@ -335,6 +348,7 @@ Message types
>
>        Id: 5
>        Equivalent ioctl: VHOST_SET_MEM_TABLE
> +      Initiator: Master
>        Master payload: memory regions description
>
>        Sets the memory map regions on the slave so it can translate the
> vring
> @@ -346,6 +360,7 @@ Message types
>
>        Id: 6
>        Equivalent ioctl: VHOST_SET_LOG_BASE
> +      Initiator: Master
>        Master payload: u64
>        Slave payload: N/A
>
> @@ -360,6 +375,7 @@ Message types
>
>        Id: 7
>        Equivalent ioctl: VHOST_SET_LOG_FD
> +      Initiator: Master
>        Master payload: N/A
>
>        Sets the logging file descriptor, which is passed as ancillary data.
> @@ -368,6 +384,7 @@ Message types
>
>        Id: 8
>        Equivalent ioctl: VHOST_SET_VRING_NUM
> +      Initiator: Master
>        Master payload: vring state description
>
>        Set the size of the queue.
> @@ -376,6 +393,7 @@ Message types
>
>        Id: 9
>        Equivalent ioctl: VHOST_SET_VRING_ADDR
> +      Initiator: Master
>        Master payload: vring address description
>        Slave payload: N/A
>
> @@ -385,6 +403,7 @@ Message types
>
>        Id: 10
>        Equivalent ioctl: VHOST_SET_VRING_BASE
> +      Initiator: Master
>        Master payload: vring state description
>
>        Sets the base offset in the available vring.
> @@ -393,6 +412,7 @@ Message types
>
>        Id: 11
>        Equivalent ioctl: VHOST_USER_GET_VRING_BASE
> +      Initiator: Master
>        Master payload: vring state description
>        Slave payload: vring state description
>
> @@ -402,6 +422,7 @@ Message types
>
>        Id: 12
>        Equivalent ioctl: VHOST_SET_VRING_KICK
> +      Initiator: Master
>        Master payload: u64
>
>        Set the event file descriptor for adding buffers to the vring. It
> @@ -415,6 +436,7 @@ Message types
>
>        Id: 13
>        Equivalent ioctl: VHOST_SET_VRING_CALL
> +      Initiator: Master
>        Master payload: u64
>
>        Set the event file descriptor to signal when buffers are used. It
> @@ -428,6 +450,7 @@ Message types
>
>        Id: 14
>        Equivalent ioctl: VHOST_SET_VRING_ERR
> +      Initiator: Master
>        Master payload: u64
>
>        Set the event file descriptor to signal when error occurs. It
> @@ -440,6 +463,7 @@ Message types
>
>        Id: 17
>        Equivalent ioctl: N/A
> +      Initiator: Master
>        Master payload: N/A
>        Slave payload: u64
>
> @@ -451,6 +475,7 @@ Message types
>
>        Id: 18
>        Equivalent ioctl: N/A
> +      Initiator: Master
>        Master payload: vring state description
>
>        Signal slave to enable or disable corresponding vring.
> @@ -461,6 +486,7 @@ Message types
>
>        Id: 19
>        Equivalent ioctl: N/A
> +      Initiator: Master
>        Master payload: u64
>
>        Ask vhost user backend to broadcast a fake RARP to notify the
> migration
> @@ -475,6 +501,7 @@ Message types
>
>        Id: 20
>        Equivalent ioctl: N/A
> +      Initiator: Master
>        Master payload: u64
>
>        Set host MTU value exposed to the guest.
> @@ -486,6 +513,17 @@ Message types
>        If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, slave must respond
>        with zero in case the specified MTU is valid, or non-zero otherwise.
>
> + * VHOST_USER_SET_SLAVE_REQ_FD
> +
> +      Id: 21
> +      Equivalent ioctl: N/A
> +      Initiator: Master
> +
> +      Set the socket file descriptor for slave initiated requests.
> +      This request should be sent only when VHOST_USER_F_PROTOCOL_FEATURES
> +      has been negotiated, and protocol feature bit
> VHOST_USER_PROTOCOL_F_SLAVE_REQ
> +      bit is present in VHOST_USER_GET_PROTOCOL_FEATURES.
> +
>

looks good to me


>  VHOST_USER_PROTOCOL_F_REPLY_ACK:
>  -------------------------------
>  The original vhost-user specification only demands replies for certain
> --
> 2.9.3
>
>
> --
Marc-André Lureau