Add vhost-user protocol feature
VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT
Now on GET_VRING_BASE this feature can control whether to wait for
in-flight requests to complete or not.
It will be helpfull in future for in-flight requests migration in
vhost-user devices.
Signed-off-by: Alexandr Moshkov <dtalexundeer@yandex-team.ru>
---
docs/interop/vhost-user.rst | 52 ++++++++++++++++++----------------
include/hw/virtio/vhost-user.h | 1 +
2 files changed, 29 insertions(+), 24 deletions(-)
diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
index 02908b48fa..80c80aada5 100644
--- a/docs/interop/vhost-user.rst
+++ b/docs/interop/vhost-user.rst
@@ -1033,26 +1033,27 @@ Protocol features
.. code:: c
- #define VHOST_USER_PROTOCOL_F_MQ 0
- #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1
- #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_BACKEND_REQ 5
- #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
- #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
- #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
- #define VHOST_USER_PROTOCOL_F_CONFIG 9
- #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10
- #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
- #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
- #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13
- #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14
- #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15
- #define VHOST_USER_PROTOCOL_F_STATUS 16
- #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17
- #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18
- #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19
+ #define VHOST_USER_PROTOCOL_F_MQ 0
+ #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1
+ #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_BACKEND_REQ 5
+ #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6
+ #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
+ #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8
+ #define VHOST_USER_PROTOCOL_F_CONFIG 9
+ #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10
+ #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11
+ #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12
+ #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13
+ #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14
+ #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15
+ #define VHOST_USER_PROTOCOL_F_STATUS 16
+ #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17
+ #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18
+ #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19
+ #define VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT 20
Front-end message types
-----------------------
@@ -1243,11 +1244,14 @@ Front-end message types
When and as long as all of a device's vrings are stopped, it is
*suspended*, see :ref:`Suspended device state
- <suspended_device_state>`. The back-end must complete all inflight I/O
- requests for the specified vring before stopping it.
+ <suspended_device_state>`.
- The request payload's *num* field is currently reserved and must be
- set to 0.
+ By default, the back-end must complete all inflight I/O requests for the
+ specified vring before stopping it.
+
+ If the ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol feature
+ has been negotiated, the back-end may stop the vring immediately without
+ waiting for inflight I/O requests to complete.
``VHOST_USER_SET_VRING_KICK``
:id: 12
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index fb89268de2..493fbce8b1 100644
--- a/include/hw/virtio/vhost-user.h
+++ b/include/hw/virtio/vhost-user.h
@@ -33,6 +33,7 @@ enum VhostUserProtocolFeature {
/* Feature 17 reserved for VHOST_USER_PROTOCOL_F_XEN_MMAP. */
VHOST_USER_PROTOCOL_F_SHARED_OBJECT = 18,
VHOST_USER_PROTOCOL_F_DEVICE_STATE = 19,
+ VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT = 20,
VHOST_USER_PROTOCOL_F_MAX
};
--
2.34.1On Mon, Jan 12, 2026 at 04:45:00PM +0500, Alexandr Moshkov wrote: > Add vhost-user protocol feature > VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT > > Now on GET_VRING_BASE this feature can control whether to wait for > in-flight requests to complete or not. > > It will be helpfull in future for in-flight requests migration in > vhost-user devices. > > Signed-off-by: Alexandr Moshkov <dtalexundeer@yandex-team.ru> > --- > docs/interop/vhost-user.rst | 52 ++++++++++++++++++---------------- > include/hw/virtio/vhost-user.h | 1 + > 2 files changed, 29 insertions(+), 24 deletions(-) > > diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst > index 02908b48fa..80c80aada5 100644 > --- a/docs/interop/vhost-user.rst > +++ b/docs/interop/vhost-user.rst > @@ -1033,26 +1033,27 @@ Protocol features > > .. code:: c > > - #define VHOST_USER_PROTOCOL_F_MQ 0 > - #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1 > - #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_BACKEND_REQ 5 > - #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6 > - #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7 > - #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8 > - #define VHOST_USER_PROTOCOL_F_CONFIG 9 > - #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10 > - #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11 > - #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12 > - #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13 > - #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14 > - #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15 > - #define VHOST_USER_PROTOCOL_F_STATUS 16 > - #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 > - #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 > - #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 > + #define VHOST_USER_PROTOCOL_F_MQ 0 > + #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1 > + #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_BACKEND_REQ 5 > + #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6 > + #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7 > + #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8 > + #define VHOST_USER_PROTOCOL_F_CONFIG 9 > + #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10 > + #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11 > + #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12 > + #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13 > + #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14 > + #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15 > + #define VHOST_USER_PROTOCOL_F_STATUS 16 > + #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 > + #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 > + #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 > + #define VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT 20 > > Front-end message types > ----------------------- > @@ -1243,11 +1244,14 @@ Front-end message types > > When and as long as all of a device's vrings are stopped, it is > *suspended*, see :ref:`Suspended device state > - <suspended_device_state>`. The back-end must complete all inflight I/O > - requests for the specified vring before stopping it. > + <suspended_device_state>`. > > - The request payload's *num* field is currently reserved and must be > - set to 0. > + By default, the back-end must complete all inflight I/O requests for the > + specified vring before stopping it. > + > + If the ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol feature > + has been negotiated, the back-end may stop the vring immediately without > + waiting for inflight I/O requests to complete. This paragraph is not specific enough. It gives the impression that I/O requests can be left running, but that's not the case. They need to be quiesced and recorded in the Inflight I/O Tracking (VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD) shared memory data structure. I suggest rewording it as follows: If the ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol feature has been negotiated, the back-end may suspend in-flight I/O requests and record them as described in :ref:`inflight-io-tracking` instead of completing them before stopping the vring. How to suspend an in-flight request depends on the implementation of the back-end but it typically can be done by aborting or cancelling the underlying I/O request. The ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol feature must only be neogotiated if ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD`` is also negotiated. (A _inflight-io-tracking label needs to be added in order to reference the "Inflight I/O tracking" section.)
On 1/12/26 23:08, Stefan Hajnoczi wrote: > On Mon, Jan 12, 2026 at 04:45:00PM +0500, Alexandr Moshkov wrote: >> Add vhost-user protocol feature >> VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT >> >> Now on GET_VRING_BASE this feature can control whether to wait for >> in-flight requests to complete or not. >> >> It will be helpfull in future for in-flight requests migration in >> vhost-user devices. >> >> Signed-off-by: Alexandr Moshkov<dtalexundeer@yandex-team.ru> >> --- >> docs/interop/vhost-user.rst | 52 ++++++++++++++++++---------------- >> include/hw/virtio/vhost-user.h | 1 + >> 2 files changed, 29 insertions(+), 24 deletions(-) >> >> diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst >> index 02908b48fa..80c80aada5 100644 >> --- a/docs/interop/vhost-user.rst >> +++ b/docs/interop/vhost-user.rst >> @@ -1033,26 +1033,27 @@ Protocol features >> >> .. code:: c >> >> - #define VHOST_USER_PROTOCOL_F_MQ 0 >> - #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1 >> - #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_BACKEND_REQ 5 >> - #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6 >> - #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7 >> - #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8 >> - #define VHOST_USER_PROTOCOL_F_CONFIG 9 >> - #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10 >> - #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11 >> - #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12 >> - #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13 >> - #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14 >> - #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15 >> - #define VHOST_USER_PROTOCOL_F_STATUS 16 >> - #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 >> - #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 >> - #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 >> + #define VHOST_USER_PROTOCOL_F_MQ 0 >> + #define VHOST_USER_PROTOCOL_F_LOG_SHMFD 1 >> + #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_BACKEND_REQ 5 >> + #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN 6 >> + #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7 >> + #define VHOST_USER_PROTOCOL_F_PAGEFAULT 8 >> + #define VHOST_USER_PROTOCOL_F_CONFIG 9 >> + #define VHOST_USER_PROTOCOL_F_BACKEND_SEND_FD 10 >> + #define VHOST_USER_PROTOCOL_F_HOST_NOTIFIER 11 >> + #define VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD 12 >> + #define VHOST_USER_PROTOCOL_F_RESET_DEVICE 13 >> + #define VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS 14 >> + #define VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS 15 >> + #define VHOST_USER_PROTOCOL_F_STATUS 16 >> + #define VHOST_USER_PROTOCOL_F_XEN_MMAP 17 >> + #define VHOST_USER_PROTOCOL_F_SHARED_OBJECT 18 >> + #define VHOST_USER_PROTOCOL_F_DEVICE_STATE 19 >> + #define VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT 20 >> >> Front-end message types >> ----------------------- >> @@ -1243,11 +1244,14 @@ Front-end message types >> >> When and as long as all of a device's vrings are stopped, it is >> *suspended*, see :ref:`Suspended device state >> - <suspended_device_state>`. The back-end must complete all inflight I/O >> - requests for the specified vring before stopping it. >> + <suspended_device_state>`. >> >> - The request payload's *num* field is currently reserved and must be >> - set to 0. >> + By default, the back-end must complete all inflight I/O requests for the >> + specified vring before stopping it. >> + >> + If the ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol feature >> + has been negotiated, the back-end may stop the vring immediately without >> + waiting for inflight I/O requests to complete. > This paragraph is not specific enough. It gives the impression that I/O > requests can be left running, but that's not the case. They need to be > quiesced and recorded in the Inflight I/O Tracking > (VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD) shared memory data structure. > > I suggest rewording it as follows: > > If the ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` protocol > feature has been negotiated, the back-end may suspend in-flight I/O > requests and record them as described in :ref:`inflight-io-tracking` > instead of completing them before stopping the vring. How to suspend > an in-flight request depends on the implementation of the back-end but > it typically can be done by aborting or cancelling the underlying I/O > request. The ``VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT`` > protocol feature must only be neogotiated if > ``VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD`` is also negotiated. > > (A _inflight-io-tracking label needs to be added in order to reference > the "Inflight I/O tracking" section.) I'll fix that, thanks!
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