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vhost-user: introduce protocol feature for skip drain on GET_VRING_BASE

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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 <dtalexundeer@yandex-team.ru>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20260115081103.655749-3-dtalexundeer@yandex-team.ru>
This commit is contained in:
Alexandr Moshkov
2026-01-15 13:11:03 +05:00
committed by Michael S. Tsirkin
parent e7985b6a56
commit e0822e6085
3 changed files with 46 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

59
docs/interop/vhost-user.rst
View File

@@ -743,6 +743,8 @@ 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
---------------------
@@ -1040,26 +1042,27 @@ 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
-----------------------
@@ -1250,12 +1253,24 @@ 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``

7
hw/virtio/vhost-user.c
View File

@@ -2225,6 +2225,13 @@ static int vhost_user_backend_init(struct vhost_dev *dev, void *opaque,
}
}
if (!u->user->supports_inflight_migration ||
!virtio_has_feature(protocol_features,
VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD)) {
protocol_features &= ~(1ULL <<
VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT);
}
/* final set of protocol features */
dev->protocol_features = protocol_features;
err = vhost_user_set_protocol_features(dev, dev->protocol_features);

2
include/hw/virtio/vhost-user.h
View File

@@ -32,6 +32,7 @@ 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
};
@@ -68,6 +69,7 @@ typedef struct VhostUserState {
GPtrArray *notifiers;
int memory_slots;
bool supports_config;
bool supports_inflight_migration;
} VhostUserState;
/**