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vhost-user: back SET/GET_CONFIG requests with a protocol feature

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Without a dedicated protocol feature, QEMU cannot know whether
the backend can handle VHOST_USER_SET_CONFIG and
VHOST_USER_GET_CONFIG messages.

This patch adds a protocol feature that is only advertised by
QEMU if the device implements the config ops. Vhost user init
fails if the device support the feature but the backend doesn't.

The backend should only send VHOST_USER_SLAVE_CONFIG_CHANGE_MSG
requests if the protocol feature has been negotiated.

Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Changpeng Liu <changpeng.liu@intel.com>
This commit is contained in:
Maxime Coquelin 2018-03-29 09:52:33 +02:00 committed by Michael S. Tsirkin
parent bc6abcff7c
commit 1c3e5a2617
2 changed files with 34 additions and 9 deletions
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21
docs/interop/vhost-user.txt
View File

@ -379,6 +379,7 @@ Protocol features
#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
Master message types
--------------------
@ -664,7 +665,8 @@ Master message types
Master payload: virtio device config space
Slave payload: virtio device config space
Submitted by the vhost-user master to fetch the contents of the virtio
When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, this message is
submitted by the vhost-user master to fetch the contents of the virtio
device configuration space, vhost-user slave's payload size MUST match
master's request, vhost-user slave uses zero length of payload to
indicate an error to vhost-user master. The vhost-user master may
@ -677,7 +679,8 @@ Master message types
Master payload: virtio device config space
Slave payload: N/A
Submitted by the vhost-user master when the Guest changes the virtio
When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, this message is
submitted by the vhost-user master when the Guest changes the virtio
device configuration space and also can be used for live migration
on the destination host. The vhost-user slave must check the flags
field, and slaves MUST NOT accept SET_CONFIG for read-only
@ -766,13 +769,13 @@ Slave message types
Slave payload: N/A
Master payload: N/A
Vhost-user slave sends such messages to notify that the virtio device's
configuration space has changed, for those host devices which can support
such feature, host driver can send VHOST_USER_GET_CONFIG message to slave
to get the latest content. If VHOST_USER_PROTOCOL_F_REPLY_ACK is
negotiated, and slave set the VHOST_USER_NEED_REPLY flag, master must
respond with zero when operation is successfully completed, or non-zero
otherwise.
When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, vhost-user slave sends
such messages to notify that the virtio device's configuration space has
changed, for those host devices which can support such feature, host
driver can send VHOST_USER_GET_CONFIG message to slave to get the latest
content. If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, and slave set
the VHOST_USER_NEED_REPLY flag, master must respond with zero when
operation is successfully completed, or non-zero otherwise.
VHOST_USER_PROTOCOL_F_REPLY_ACK:
-------------------------------

22
hw/virtio/vhost-user.c
View File

@ -46,6 +46,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
VHOST_USER_PROTOCOL_F_CONFIG = 9,
VHOST_USER_PROTOCOL_F_MAX
};
@ -1211,6 +1212,17 @@ static int vhost_user_init(struct vhost_dev *dev, void *opaque)
dev->protocol_features =
protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK;
if (!dev->config_ops || !dev->config_ops->vhost_dev_config_notifier) {
/* Don't acknowledge CONFIG feature if device doesn't support it */
dev->protocol_features &= ~(1ULL << VHOST_USER_PROTOCOL_F_CONFIG);
} else if (!(protocol_features &
(1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) {
error_report("Device expects VHOST_USER_PROTOCOL_F_CONFIG "
"but backend does not support it.");
return -1;
}
err = vhost_user_set_protocol_features(dev, dev->protocol_features);
if (err < 0) {
return err;
@ -1405,6 +1417,11 @@ static int vhost_user_get_config(struct vhost_dev *dev, uint8_t *config,
.hdr.size = VHOST_USER_CONFIG_HDR_SIZE + config_len,
};
if (!virtio_has_feature(dev->protocol_features,
VHOST_USER_PROTOCOL_F_CONFIG)) {
return -1;
}
if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
return -1;
}
@ -1448,6 +1465,11 @@ static int vhost_user_set_config(struct vhost_dev *dev, const uint8_t *data,
.hdr.size = VHOST_USER_CONFIG_HDR_SIZE + size,
};
if (!virtio_has_feature(dev->protocol_features,
VHOST_USER_PROTOCOL_F_CONFIG)) {
return -1;
}
if (reply_supported) {
msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
}