On 1/13/26 23:00, Stefan Hajnoczi wrote:
On Tue, Jan 13, 2026 at 02:58:13PM +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.
Also we have to validate that this feature will be enabled only when
qemu and back-end supports in-flight buffer and in-flight migration
It will be helpfull in future for in-flight requests migration in
vhost-user devices.
Update docs, add ref to label for inflight-io-tracking
Signed-off-by: Alexandr Moshkov<[email protected]>
---
docs/interop/vhost-user.rst | 59 +++++++++++++++++++++-------------
hw/virtio/vhost-user.c | 5 +++
include/hw/virtio/vhost-user.h | 2 ++
3 files changed, 44 insertions(+), 22 deletions(-)
diff --git a/docs/interop/vhost-user.rst b/docs/interop/vhost-user.rst
index 02908b48fa..dcf79de0c0 100644
--- a/docs/interop/vhost-user.rst
+++ b/docs/interop/vhost-user.rst
@@ -736,6 +736,8 @@ negotiated, back-end can send file descriptors (at most 8
descriptors in
each message) to front-end via ancillary data using this fd communication
channel.
+.. _inflight_io_tracking:
+
Inflight I/O tracking
---------------------
@@ -1033,26 +1035,27 @@ 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
-----------------------
@@ -1243,12 +1246,24 @@ 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 suspend in-flight I/O
+ requests and record them as described in :ref:`Inflight I/O tracking
+ <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.
+
``VHOST_USER_SET_VRING_KICK``
:id: 12
:equivalent ioctl: ``VHOST_SET_VRING_KICK``
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index a820214188..793d1b36d8 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -2320,6 +2320,11 @@ static int vhost_user_backend_connect(struct vhost_dev
*dev, Error **errp)
}
}
+ if (!u->user->supports_inflight_migration ||
+ !virtio_has_feature(VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
This looks like it will not compile since virtio_has_features() takes
two arguments. I think it should be:
!virtio_has_feature(dev->protocol_features,
VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)
Oh, how did I miss that...
I'll fix it! Thanks
+ protocol_features &= ~(1ULL <<
+ VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT);
+ }
+
/* final set of protocol features */
u->protocol_features = protocol_features;
err = vhost_user_set_protocol_features(dev, u->protocol_features);
I seem to have different version of hw/virtio/vhost-user.c. Is this
patch against qemu.git/master?
This patch is based on Vladimir's patch, but I now thinks that I can
separate my patch from his.
At first I thought there would be a lot of intersections with his patch.
In the next version, I will rebase this patch on the master
diff --git a/include/hw/virtio/vhost-user.h b/include/hw/virtio/vhost-user.h
index fb89268de2..f30c1792e4 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
};
@@ -69,6 +70,7 @@ typedef struct VhostUserState {
GPtrArray *notifiers;
int memory_slots;
bool supports_config;
+ bool supports_inflight_migration;
} VhostUserState;
/**
--
2.34.1
