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authorYajun Wu <yajunw@nvidia.com>2022-10-17 14:44:52 +0800
committerMichael S. Tsirkin <mst@redhat.com>2022-11-07 14:08:17 -0500
commit923b8921d210763359e96246a58658ac0db6c645 (patch)
tree8e2d3ec4a6e21e5d244f0d94b0d547f7714843f6 /hw/virtio
parent8b67fe00652b2640f3f841a7b102f6bcf82483a3 (diff)
vhost-user: Support vhost_dev_start
The motivation of adding vhost-user vhost_dev_start support is to improve backend configuration speed and reduce live migration VM downtime. Today VQ configuration is issued one by one. For virtio net with multi-queue support, backend needs to update RSS (Receive side scaling) on every rx queue enable. Updating RSS is time-consuming (typical time like 7ms). Implement already defined vhost status and message in the vhost specification [1]. (a) VHOST_USER_PROTOCOL_F_STATUS (b) VHOST_USER_SET_STATUS (c) VHOST_USER_GET_STATUS Send message VHOST_USER_SET_STATUS with VIRTIO_CONFIG_S_DRIVER_OK for device start and reset(0) for device stop. On reception of the DRIVER_OK message, backend can apply the needed setting only once (instead of incremental) and also utilize parallelism on enabling queues. This improves QEMU's live migration downtime with vhost user backend implementation by great margin, specially for the large number of VQs of 64 from 800 msec to 250 msec. [1] https://qemu-project.gitlab.io/qemu/interop/vhost-user.html Signed-off-by: Yajun Wu <yajunw@nvidia.com> Acked-by: Parav Pandit <parav@nvidia.com> Message-Id: <20221017064452.1226514-3-yajunw@nvidia.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw/virtio')
-rw-r--r--hw/virtio/vhost-user.c74
1 files changed, 73 insertions, 1 deletions
diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
index d256ce589b..abe23d4ebe 100644
--- a/hw/virtio/vhost-user.c
+++ b/hw/virtio/vhost-user.c
@@ -81,6 +81,7 @@ enum VhostUserProtocolFeature {
VHOST_USER_PROTOCOL_F_RESET_DEVICE = 13,
/* Feature 14 reserved for VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS. */
VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
+ VHOST_USER_PROTOCOL_F_STATUS = 16,
VHOST_USER_PROTOCOL_F_MAX
};
@@ -126,6 +127,8 @@ typedef enum VhostUserRequest {
VHOST_USER_GET_MAX_MEM_SLOTS = 36,
VHOST_USER_ADD_MEM_REG = 37,
VHOST_USER_REM_MEM_REG = 38,
+ VHOST_USER_SET_STATUS = 39,
+ VHOST_USER_GET_STATUS = 40,
VHOST_USER_MAX
} VhostUserRequest;
@@ -1452,6 +1455,43 @@ static int vhost_user_set_u64(struct vhost_dev *dev, int request, uint64_t u64,
return 0;
}
+static int vhost_user_set_status(struct vhost_dev *dev, uint8_t status)
+{
+ return vhost_user_set_u64(dev, VHOST_USER_SET_STATUS, status, false);
+}
+
+static int vhost_user_get_status(struct vhost_dev *dev, uint8_t *status)
+{
+ uint64_t value;
+ int ret;
+
+ ret = vhost_user_get_u64(dev, VHOST_USER_GET_STATUS, &value);
+ if (ret < 0) {
+ return ret;
+ }
+ *status = value;
+
+ return 0;
+}
+
+static int vhost_user_add_status(struct vhost_dev *dev, uint8_t status)
+{
+ uint8_t s;
+ int ret;
+
+ ret = vhost_user_get_status(dev, &s);
+ if (ret < 0) {
+ return ret;
+ }
+
+ if ((s & status) == status) {
+ return 0;
+ }
+ s |= status;
+
+ return vhost_user_set_status(dev, s);
+}
+
static int vhost_user_set_features(struct vhost_dev *dev,
uint64_t features)
{
@@ -1460,6 +1500,7 @@ static int vhost_user_set_features(struct vhost_dev *dev,
* backend is actually logging changes
*/
bool log_enabled = features & (0x1ULL << VHOST_F_LOG_ALL);
+ int ret;
/*
* We need to include any extra backend only feature bits that
@@ -1467,9 +1508,18 @@ static int vhost_user_set_features(struct vhost_dev *dev,
* VHOST_USER_F_PROTOCOL_FEATURES bit for enabling protocol
* features.
*/
- return vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES,
+ ret = vhost_user_set_u64(dev, VHOST_USER_SET_FEATURES,
features | dev->backend_features,
log_enabled);
+
+ if (virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_STATUS)) {
+ if (!ret) {
+ return vhost_user_add_status(dev, VIRTIO_CONFIG_S_FEATURES_OK);
+ }
+ }
+
+ return ret;
}
static int vhost_user_set_protocol_features(struct vhost_dev *dev,
@@ -2620,6 +2670,27 @@ void vhost_user_cleanup(VhostUserState *user)
user->chr = NULL;
}
+static int vhost_user_dev_start(struct vhost_dev *dev, bool started)
+{
+ if (!virtio_has_feature(dev->protocol_features,
+ VHOST_USER_PROTOCOL_F_STATUS)) {
+ return 0;
+ }
+
+ /* Set device status only for last queue pair */
+ if (dev->vq_index + dev->nvqs != dev->vq_index_end) {
+ return 0;
+ }
+
+ if (started) {
+ return vhost_user_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
+ VIRTIO_CONFIG_S_DRIVER |
+ VIRTIO_CONFIG_S_DRIVER_OK);
+ } else {
+ return vhost_user_set_status(dev, 0);
+ }
+}
+
const VhostOps user_ops = {
.backend_type = VHOST_BACKEND_TYPE_USER,
.vhost_backend_init = vhost_user_backend_init,
@@ -2654,4 +2725,5 @@ const VhostOps user_ops = {
.vhost_backend_mem_section_filter = vhost_user_mem_section_filter,
.vhost_get_inflight_fd = vhost_user_get_inflight_fd,
.vhost_set_inflight_fd = vhost_user_set_inflight_fd,
+ .vhost_dev_start = vhost_user_dev_start,
};