Re: [PATCH 08/16] vhost: add op to enable or disable a single vring

[Kangjie Xu]

在 2022/7/26 11:49, Jason Wang 写道:
> 在 2022/7/18 19:17, Kangjie Xu 写道:
> > The interface to set enable status for a single vring is lacked in
> > VhostOps, since the vhost_set_vring_enable_op will manipulate all
> > virtqueues in a device.
> >
> > Resetting a single vq will rely on this interface. It requires a
> > reply to indicate that the reset operation is finished, so the
> > parameter, wait_for_reply, is added.
>
>
> The wait reply seems to be a implementation specific thing. Can we 
> hide it?
>
> Thanks
I do not hide wait_for_reply here because when stopping the queue, a 
reply is needed to ensure that the message has been processed and queue 
has been disabled.

When restarting the queue, we do not need a reply, which is the same as 
what qemu does in vhost_dev_start().

So I add this parameter to distinguish the two cases.

I think one alternative implementation is to add a interface in 
VhostOps: queue_reset(). In this way details can be hidden. What do you 
think of this solution? Does it look better?

Thanks

> > Signed-off-by: Kangjie Xu <kangjie.xu@linux.alibaba.com>
> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com>
> > ---
> >   include/hw/virtio/vhost-backend.h | 4 ++++
> >   1 file changed, 4 insertions(+)
> >
> > diff --git a/include/hw/virtio/vhost-backend.h 
> > b/include/hw/virtio/vhost-backend.h
> > index eab46d7f0b..7bddd1e9a0 100644
> > --- a/include/hw/virtio/vhost-backend.h
> > +++ b/include/hw/virtio/vhost-backend.h
> > @@ -81,6 +81,9 @@ typedef int (*vhost_set_backend_cap_op)(struct 
> > vhost_dev *dev);
> >   typedef int (*vhost_set_owner_op)(struct vhost_dev *dev);
> >   typedef int (*vhost_reset_device_op)(struct vhost_dev *dev);
> >   typedef int (*vhost_get_vq_index_op)(struct vhost_dev *dev, int idx);
> > +typedef int (*vhost_set_single_vring_enable_op)(struct vhost_dev *dev,
> > +                                                int index, int enable,
> > +                                                bool wait_for_reply);
> >   typedef int (*vhost_set_vring_enable_op)(struct vhost_dev *dev,
> >                                            int enable);
> >   typedef bool (*vhost_requires_shm_log_op)(struct vhost_dev *dev);
> > @@ -155,6 +158,7 @@ typedef struct VhostOps {
> >       vhost_set_owner_op vhost_set_owner;
> >       vhost_reset_device_op vhost_reset_device;
> >       vhost_get_vq_index_op vhost_get_vq_index;
> > +    vhost_set_single_vring_enable_op vhost_set_single_vring_enable;
> >       vhost_set_vring_enable_op vhost_set_vring_enable;
> >       vhost_requires_shm_log_op vhost_requires_shm_log;
> >       vhost_migration_done_op vhost_migration_done;