On Mon, Aug 3, 2026 at 9:30 AM Alexandr Moshkov
<[email protected]> wrote:
>
> Currently do_vhost_virtqueue_stop always sends GET_VRING_BASE to the
> back-end, which requires the back-end to drain all in-flight I/O before
> stopping the vring.
>
> Add a skip_drain parameter to do_vhost_virtqueue_stop and propagate it
> up through vhost_virtqueue_stop, vhost_dev_stop and their callers.
> The parameter will be used in a follow-up commit to send a new protocol
> message that instructs the back-end to suspend in-flight I/O immediately
> instead of draining it.
>
> Signed-off-by: Alexandr Moshkov <[email protected]>
> ---
> backends/cryptodev-vhost.c | 2 +-
> backends/vhost-user.c | 2 +-
> hw/block/vhost-user-blk.c | 2 +-
> hw/net/vhost_net.c | 9 +++++----
> hw/scsi/vhost-scsi-common.c | 2 +-
> hw/virtio/vdpa-dev.c | 2 +-
> hw/virtio/vhost-user-base.c | 2 +-
> hw/virtio/vhost-user-fs.c | 2 +-
> hw/virtio/vhost-user-scmi.c | 2 +-
> hw/virtio/vhost-vsock-common.c | 2 +-
> hw/virtio/vhost.c | 28 +++++++++++++++++++---------
> include/hw/virtio/vhost.h | 7 +++++--
> 12 files changed, 38 insertions(+), 24 deletions(-)
>
> diff --git a/backends/cryptodev-vhost.c b/backends/cryptodev-vhost.c
> index c6069f4e5b..f1ca6bcd4e 100644
> --- a/backends/cryptodev-vhost.c
> +++ b/backends/cryptodev-vhost.c
> @@ -109,7 +109,7 @@ static void
> cryptodev_vhost_stop_one(CryptoDevBackendVhost *crypto,
> VirtIODevice *dev)
> {
> - vhost_dev_stop(&crypto->dev, dev, false);
> + vhost_dev_stop(&crypto->dev, dev, false, false);
> vhost_dev_disable_notifiers(&crypto->dev, dev);
> }
>
> diff --git a/backends/vhost-user.c b/backends/vhost-user.c
> index 380d825023..0423c2d4ec 100644
> --- a/backends/vhost-user.c
> +++ b/backends/vhost-user.c
> @@ -108,7 +108,7 @@ vhost_user_backend_stop(VhostUserBackend *b)
> return 0;
> }
>
> - ret = vhost_dev_stop(&b->dev, b->vdev, true);
> + ret = vhost_dev_stop(&b->dev, b->vdev, true, false);
>
> if (k->set_guest_notifiers &&
> (err = k->set_guest_notifiers(qbus->parent, b->dev.nvqs, false)) <
> 0) {
> diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c
> index b2e46eb3f9..e3b873af7c 100644
> --- a/hw/block/vhost-user-blk.c
> +++ b/hw/block/vhost-user-blk.c
> @@ -232,7 +232,7 @@ static int vhost_user_blk_stop(VirtIODevice *vdev)
> qemu_force_shutdown_requested();
>
> ret = force_stop ? vhost_dev_force_stop(&s->dev, vdev, true) :
> - vhost_dev_stop(&s->dev, vdev, true);
> + vhost_dev_stop(&s->dev, vdev, true, false);
>
> err = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
> if (err < 0) {
> diff --git a/hw/net/vhost_net.c b/hw/net/vhost_net.c
> index 323d117735..6e05c995f1 100644
> --- a/hw/net/vhost_net.c
> +++ b/hw/net/vhost_net.c
> @@ -384,7 +384,7 @@ fail:
> if (net->nc->info->poll) {
> net->nc->info->poll(net->nc, true);
> }
> - vhost_dev_stop(&net->dev, dev, false);
> + vhost_dev_stop(&net->dev, dev, false, false);
> fail_start:
> return r;
> }
> @@ -403,7 +403,7 @@ static void vhost_net_stop_one(struct vhost_net *net,
> if (net->nc->info->poll) {
> net->nc->info->poll(net->nc, true);
> }
> - vhost_dev_stop(&net->dev, dev, false);
> + vhost_dev_stop(&net->dev, dev, false, false);
> if (net->nc->info->stop) {
> net->nc->info->stop(net->nc);
> }
> @@ -636,7 +636,8 @@ void vhost_net_virtqueue_reset(VirtIODevice *vdev,
> NetClientState *nc,
> vhost_virtqueue_stop(&net->dev,
> vdev,
> net->dev.vqs + idx,
> - net->dev.vq_index + idx);
> + net->dev.vq_index + idx,
> + false);
> }
>
> int vhost_net_virtqueue_restart(VirtIODevice *vdev, NetClientState *nc,
> @@ -686,7 +687,7 @@ err_start:
> assert(ret >= 0);
> }
>
> - vhost_dev_stop(&net->dev, vdev, false);
> + vhost_dev_stop(&net->dev, vdev, false, false);
>
> return r;
> }
> diff --git a/hw/scsi/vhost-scsi-common.c b/hw/scsi/vhost-scsi-common.c
> index e19800a0bc..e546a6dc75 100644
> --- a/hw/scsi/vhost-scsi-common.c
> +++ b/hw/scsi/vhost-scsi-common.c
> @@ -108,7 +108,7 @@ int vhost_scsi_common_stop(VHostSCSICommon *vsc)
> VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> int ret = 0;
>
> - ret = vhost_dev_stop(&vsc->dev, vdev, true);
> + ret = vhost_dev_stop(&vsc->dev, vdev, true, false);
>
> if (k->set_guest_notifiers) {
> int r = k->set_guest_notifiers(qbus->parent, vsc->dev.nvqs, false);
> diff --git a/hw/virtio/vdpa-dev.c b/hw/virtio/vdpa-dev.c
> index 94188d37bb..b86d0b664a 100644
> --- a/hw/virtio/vdpa-dev.c
> +++ b/hw/virtio/vdpa-dev.c
> @@ -300,7 +300,7 @@ static void vhost_vdpa_device_stop(VirtIODevice *vdev)
> return;
> }
>
> - vhost_dev_stop(&s->dev, vdev, false);
> + vhost_dev_stop(&s->dev, vdev, false, false);
>
> ret = k->set_guest_notifiers(qbus->parent, s->dev.nvqs, false);
> if (ret < 0) {
> diff --git a/hw/virtio/vhost-user-base.c b/hw/virtio/vhost-user-base.c
> index 39b5e637fc..abeae1a064 100644
> --- a/hw/virtio/vhost-user-base.c
> +++ b/hw/virtio/vhost-user-base.c
> @@ -78,7 +78,7 @@ static int vub_stop(VirtIODevice *vdev)
> return 0;
> }
>
> - ret = vhost_dev_stop(&vub->vhost_dev, vdev, true);
> + ret = vhost_dev_stop(&vub->vhost_dev, vdev, true, false);
>
> err = k->set_guest_notifiers(qbus->parent, vub->vhost_dev.nvqs, false);
> if (err < 0) {
> diff --git a/hw/virtio/vhost-user-fs.c b/hw/virtio/vhost-user-fs.c
> index 209993918a..0d8842817a 100644
> --- a/hw/virtio/vhost-user-fs.c
> +++ b/hw/virtio/vhost-user-fs.c
> @@ -111,7 +111,7 @@ static int vuf_stop(VirtIODevice *vdev)
> return 0;
> }
>
> - ret = vhost_dev_stop(&fs->vhost_dev, vdev, true);
> + ret = vhost_dev_stop(&fs->vhost_dev, vdev, true, false);
>
> err = k->set_guest_notifiers(qbus->parent, fs->vhost_dev.nvqs, false);
> if (err < 0) {
> diff --git a/hw/virtio/vhost-user-scmi.c b/hw/virtio/vhost-user-scmi.c
> index 9470f68c1f..9fa65d7d8b 100644
> --- a/hw/virtio/vhost-user-scmi.c
> +++ b/hw/virtio/vhost-user-scmi.c
> @@ -101,7 +101,7 @@ static int vu_scmi_stop(VirtIODevice *vdev)
> return 0;
> }
>
> - ret = vhost_dev_stop(vhost_dev, vdev, true);
> + ret = vhost_dev_stop(vhost_dev, vdev, true, false);
>
> err = k->set_guest_notifiers(qbus->parent, vhost_dev->nvqs, false);
> if (err < 0) {
> diff --git a/hw/virtio/vhost-vsock-common.c b/hw/virtio/vhost-vsock-common.c
> index b79f4c9ce6..4ef037627b 100644
> --- a/hw/virtio/vhost-vsock-common.c
> +++ b/hw/virtio/vhost-vsock-common.c
> @@ -106,7 +106,7 @@ int vhost_vsock_common_stop(VirtIODevice *vdev)
> return 0;
> }
>
> - ret = vhost_dev_stop(&vvc->vhost_dev, vdev, true);
> + ret = vhost_dev_stop(&vvc->vhost_dev, vdev, true, false);
>
> err = k->set_guest_notifiers(qbus->parent, vvc->vhost_dev.nvqs, false);
> if (err < 0) {
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index af41841b52..2a62550222 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -23,6 +23,7 @@
> #include "qemu/log.h"
> #include "standard-headers/linux/vhost_types.h"
> #include "hw/virtio/virtio-bus.h"
> +#include "hw/virtio/vhost-user.h"
> #include "hw/mem/memory-device.h"
> #include "migration/blocker.h"
> #include "migration/qemu-file-types.h"
> @@ -1496,8 +1497,13 @@ fail:
> static int do_vhost_virtqueue_stop(struct vhost_dev *dev,
> struct VirtIODevice *vdev,
> struct vhost_virtqueue *vq,
> - unsigned idx, bool force)
> + unsigned idx, bool force,
> + bool skip_drain)
> {
> + if (skip_drain) {
> + assert(vhost_user_has_protocol_feature(dev,
> + VHOST_USER_PROTOCOL_F_GET_VRING_BASE_INFLIGHT));
> + }
FYI, with only `--disable-vhost-user` configuration, this line
triggers a link error:
| undefined reference to `vhost_user_has_protocol_feature'
Disabling all vhosts (so vhost-user, vhost-vdpa and vhost-kernel) was
enough to fix it.
Clément
> int vhost_vq_index = dev->vhost_ops->vhost_get_vq_index(dev, idx);
> struct vhost_vring_state state = {
> .index = vhost_vq_index,
> @@ -1547,9 +1553,10 @@ static int do_vhost_virtqueue_stop(struct vhost_dev
> *dev,
> int vhost_virtqueue_stop(struct vhost_dev *dev,
> struct VirtIODevice *vdev,
> struct vhost_virtqueue *vq,
> - unsigned idx)
> + unsigned idx,
> + bool skip_drain)
> {
> - return do_vhost_virtqueue_stop(dev, vdev, vq, idx, false);
> + return do_vhost_virtqueue_stop(dev, vdev, vq, idx, false, skip_drain);
> }
>
> static int vhost_virtqueue_set_busyloop_timeout(struct vhost_dev *dev,
> @@ -2302,7 +2309,8 @@ fail_vq:
> vhost_virtqueue_stop(hdev,
> vdev,
> hdev->vqs + i,
> - hdev->vq_index + i);
> + hdev->vq_index + i,
> + false);
> }
>
> fail_mem:
> @@ -2317,7 +2325,7 @@ fail_features:
>
> /* Host notifiers must be enabled at this point. */
> static int do_vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev,
> - bool vrings, bool force)
> + bool vrings, bool force, bool skip_drain)
> {
> int i;
> int rc = 0;
> @@ -2344,7 +2352,8 @@ static int do_vhost_dev_stop(struct vhost_dev *hdev,
> VirtIODevice *vdev,
> vdev,
> hdev->vqs + i,
> hdev->vq_index + i,
> - force);
> + force,
> + skip_drain);
> }
> if (hdev->vhost_ops->vhost_reset_status) {
> hdev->vhost_ops->vhost_reset_status(hdev);
> @@ -2366,15 +2375,16 @@ static int do_vhost_dev_stop(struct vhost_dev *hdev,
> VirtIODevice *vdev,
> return rc;
> }
>
> -int vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings)
> +int vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings,
> + bool skip_drain)
> {
> - return do_vhost_dev_stop(hdev, vdev, vrings, false);
> + return do_vhost_dev_stop(hdev, vdev, vrings, false, skip_drain);
> }
>
> int vhost_dev_force_stop(struct vhost_dev *hdev, VirtIODevice *vdev,
> bool vrings)
> {
> - return do_vhost_dev_stop(hdev, vdev, vrings, true);
> + return do_vhost_dev_stop(hdev, vdev, vrings, true, false);
> }
>
> int vhost_net_set_backend(struct vhost_dev *hdev,
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index 684bafcaad..33b88f95ea 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -228,6 +228,7 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice
> *vdev, bool vrings);
> * @hdev: common vhost_dev structure
> * @vdev: the VirtIODevice structure
> * @vrings: true to have vrings disabled in this call
> + * @skip_drain: true to notice back-end to skip draining all in-flight
> requests
> *
> * Stop the vhost device. After the device is stopped the notifiers
> * can be disabled (@vhost_dev_disable_notifiers) and the device can
> @@ -235,7 +236,8 @@ int vhost_dev_start(struct vhost_dev *hdev, VirtIODevice
> *vdev, bool vrings);
> *
> * Return: 0 on success, != 0 on error when stopping dev.
> */
> -int vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings);
> +int vhost_dev_stop(struct vhost_dev *hdev, VirtIODevice *vdev, bool vrings,
> + bool skip_drain);
>
> /**
> * vhost_dev_force_stop() - force stop the vhost device
> @@ -393,7 +395,8 @@ int vhost_device_iotlb_miss(struct vhost_dev *dev,
> uint64_t iova, int write);
> int vhost_virtqueue_start(struct vhost_dev *dev, struct VirtIODevice *vdev,
> struct vhost_virtqueue *vq, unsigned idx);
> int vhost_virtqueue_stop(struct vhost_dev *dev, struct VirtIODevice *vdev,
> - struct vhost_virtqueue *vq, unsigned idx);
> + struct vhost_virtqueue *vq, unsigned idx,
> + bool skip_drain);
>
> void vhost_dev_reset_inflight(struct vhost_inflight *inflight);
> void vhost_dev_free_inflight(struct vhost_inflight *inflight);
> --
> 2.34.1
>
>
