On Fri, Jan 13, 2023 at 5:10 AM Jason Wang <jasow...@redhat.com> wrote:
>
> On Fri, Jan 13, 2023 at 1:24 AM Eugenio Pérez <epere...@redhat.com> wrote:
> >
> > At this moment it is only possible to migrate to a vdpa device running
> > with x-svq=on. As a protective measure, the rewind of the inflight
> > descriptors was done at the destination. That way if the source sent a
> > virtqueue with inuse descriptors they are always discarded.
> >
> > Since this series allows to migrate also to passthrough devices with no
> > SVQ, the right thing to do is to rewind at the source so base of vrings
> > are correct.
> >
> > Support for inflight descriptors may be added in the future.
> >
> > Signed-off-by: Eugenio Pérez <epere...@redhat.com>
> > ---
> > include/hw/virtio/vhost-backend.h | 4 +++
> > hw/virtio/vhost-vdpa.c | 46 +++++++++++++++++++------------
> > hw/virtio/vhost.c | 3 ++
> > 3 files changed, 36 insertions(+), 17 deletions(-)
> >
> > diff --git a/include/hw/virtio/vhost-backend.h
> > b/include/hw/virtio/vhost-backend.h
> > index c5ab49051e..ec3fbae58d 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -130,6 +130,9 @@ typedef bool (*vhost_force_iommu_op)(struct vhost_dev
> > *dev);
> >
> > typedef int (*vhost_set_config_call_op)(struct vhost_dev *dev,
> > int fd);
> > +
> > +typedef void (*vhost_reset_status_op)(struct vhost_dev *dev);
> > +
> > typedef struct VhostOps {
> > VhostBackendType backend_type;
> > vhost_backend_init vhost_backend_init;
> > @@ -177,6 +180,7 @@ typedef struct VhostOps {
> > vhost_get_device_id_op vhost_get_device_id;
> > vhost_force_iommu_op vhost_force_iommu;
> > vhost_set_config_call_op vhost_set_config_call;
> > + vhost_reset_status_op vhost_reset_status;
> > } VhostOps;
> >
> > int vhost_backend_update_device_iotlb(struct vhost_dev *dev,
> > diff --git a/hw/virtio/vhost-vdpa.c b/hw/virtio/vhost-vdpa.c
> > index 542e003101..28a52ddc78 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1132,14 +1132,23 @@ static int vhost_vdpa_dev_start(struct vhost_dev
> > *dev, bool started)
> > if (started) {
> > memory_listener_register(&v->listener, &address_space_memory);
> > return vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_DRIVER_OK);
> > - } else {
> > - vhost_vdpa_reset_device(dev);
> > - vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> > - VIRTIO_CONFIG_S_DRIVER);
> > - memory_listener_unregister(&v->listener);
> > + }
> >
> > - return 0;
> > + return 0;
> > +}
> > +
> > +static void vhost_vdpa_reset_status(struct vhost_dev *dev)
> > +{
> > + struct vhost_vdpa *v = dev->opaque;
> > +
> > + if (dev->vq_index + dev->nvqs != dev->vq_index_end) {
> > + return;
> > }
> > +
> > + vhost_vdpa_reset_device(dev);
> > + vhost_vdpa_add_status(dev, VIRTIO_CONFIG_S_ACKNOWLEDGE |
> > + VIRTIO_CONFIG_S_DRIVER);
> > + memory_listener_unregister(&v->listener);
> > }
> >
> > static int vhost_vdpa_set_log_base(struct vhost_dev *dev, uint64_t base,
> > @@ -1182,18 +1191,7 @@ static int vhost_vdpa_set_vring_base(struct
> > vhost_dev *dev,
> > struct vhost_vring_state *ring)
> > {
> > struct vhost_vdpa *v = dev->opaque;
> > - VirtQueue *vq = virtio_get_queue(dev->vdev, ring->index);
> >
> > - /*
> > - * vhost-vdpa devices does not support in-flight requests. Set all of
> > them
> > - * as available.
> > - *
> > - * TODO: This is ok for networking, but other kinds of devices might
> > - * have problems with these retransmissions.
> > - */
> > - while (virtqueue_rewind(vq, 1)) {
> > - continue;
> > - }
> > if (v->shadow_vqs_enabled) {
> > /*
> > * Device vring base was set at device start. SVQ base is handled
> > by
> > @@ -1212,6 +1210,19 @@ static int vhost_vdpa_get_vring_base(struct
> > vhost_dev *dev,
> > int ret;
> >
> > if (v->shadow_vqs_enabled) {
> > + VirtQueue *vq = virtio_get_queue(dev->vdev, ring->index);
> > +
> > + /*
> > + * vhost-vdpa devices does not support in-flight requests. Set all
> > of
> > + * them as available.
> > + *
> > + * TODO: This is ok for networking, but other kinds of devices
> > might
> > + * have problems with these retransmissions.
> > + */
> > + while (virtqueue_rewind(vq, 1)) {
> > + continue;
> > + }
> > +
> > ring->num = virtio_queue_get_last_avail_idx(dev->vdev,
> > ring->index);
> > return 0;
> > }
> > @@ -1326,4 +1337,5 @@ const VhostOps vdpa_ops = {
> > .vhost_vq_get_addr = vhost_vdpa_vq_get_addr,
> > .vhost_force_iommu = vhost_vdpa_force_iommu,
> > .vhost_set_config_call = vhost_vdpa_set_config_call,
> > + .vhost_reset_status = vhost_vdpa_reset_status,
>
> Can we simply use the NetClient stop method here?
>
Ouch, I squashed two patches by mistake here.
All the vhost_reset_status part should be independent of this patch,
and I was especially interested in its feedback. It had this message:
vdpa: move vhost reset after get vring base
The function vhost.c:vhost_dev_stop calls vhost operation
vhost_dev_start(false). In the case of vdpa it totally reset and wipes
the device, making the fetching of the vring base (virtqueue state) totally
useless.
The kernel backend does not use vhost_dev_start vhost op callback, but
vhost-user do. A patch to make vhost_user_dev_start more similar to vdpa
is desirable, but it can be added on top.
I can resend the series splitting it again but conversation may
scatter between versions. Would you prefer me to send a new version?
Regarding the use of NetClient, it feels weird to call net specific
functions in VhostOps, doesn't it? At the moment vhost ops is
specialized in vhost-kernel, vhost-user and vhost-vdpa. If we want to
make it specific to the kind of device, that makes vhost-vdpa-net too.
Thanks!
> Thanks
>
> > };
> > diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> > index eb8c4c378c..a266396576 100644
> > --- a/hw/virtio/vhost.c
> > +++ b/hw/virtio/vhost.c
> > @@ -2049,6 +2049,9 @@ void vhost_dev_stop(struct vhost_dev *hdev,
> > VirtIODevice *vdev, bool vrings)
> > hdev->vqs + i,
> > hdev->vq_index + i);
> > }
> > + if (hdev->vhost_ops->vhost_reset_status) {
> > + hdev->vhost_ops->vhost_reset_status(hdev);
> > + }
> >
> > if (vhost_dev_has_iommu(hdev)) {
> > if (hdev->vhost_ops->vhost_set_iotlb_callback) {
> > --
> > 2.31.1
> >
>
