Re: [PATCH v4 05/15] vdpa: move vhost reset after get vring base

[Eugenio Perez Martin]

On Mon, Feb 27, 2023 at 8:22 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2023/2/24 23:54, Eugenio Pérez 写道:
> > 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.
>
>
> As discussed before, should we do something reverse: in
> vhost_vdpa_dev_started() since what proposed in the patch doesn't solve
> the issue (index could be moved after the get_vring_base())
>
> 1) if _F_SUSPEND is negotiated, suspend instead of reset
>
> 2) if _F_SUSPEND is not negotiated, reset and fail
> vhost_get_vring_base() to allow graceful fallback?
>

Right. I think option 2 is the right one, as it introduces the changes
more gradually.

Thanks!

> Thanks
>
>
> >
> > 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.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> >   include/hw/virtio/vhost-backend.h |  4 ++++
> >   hw/virtio/vhost-vdpa.c            | 22 ++++++++++++++++------
> >   hw/virtio/vhost.c                 |  3 +++
> >   3 files changed, 23 insertions(+), 6 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 4fac144169..8cc9c98db9 100644
> > --- a/hw/virtio/vhost-vdpa.c
> > +++ b/hw/virtio/vhost-vdpa.c
> > @@ -1134,14 +1134,23 @@ 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,
> > @@ -1328,4 +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,
> >   };
> > 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) {
>