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SubjectRe: [PATCH v6 2/4] vhost-vdpa: introduce SUSPEND backend feature bit
On Wed, Jun 29, 2022 at 6:12 AM Jason Wang <jasowang@redhat.com> wrote:
>
> On Fri, Jun 24, 2022 at 12:08 AM Eugenio Pérez <eperezma@redhat.com> wrote:
> >
> > Userland knows if it can suspend the device or not by checking this feature
> > bit.
> >
> > It's only offered if the vdpa driver backend implements the suspend()
> > operation callback, and to offer it or userland to ack it if the backend
> > does not offer that callback is an error.
> >
> > Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> > ---
> > drivers/vhost/vdpa.c | 16 +++++++++++++++-
> > include/uapi/linux/vhost_types.h | 2 ++
> > 2 files changed, 17 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > index 23dcbfdfa13b..3d636e192061 100644
> > --- a/drivers/vhost/vdpa.c
> > +++ b/drivers/vhost/vdpa.c
> > @@ -347,6 +347,14 @@ static long vhost_vdpa_set_config(struct vhost_vdpa *v,
> > return 0;
> > }
> >
> > +static bool vhost_vdpa_can_suspend(const struct vhost_vdpa *v)
> > +{
> > + struct vdpa_device *vdpa = v->vdpa;
> > + const struct vdpa_config_ops *ops = vdpa->config;
> > +
> > + return ops->suspend;
> > +}
> > +
> > static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
> > {
> > struct vdpa_device *vdpa = v->vdpa;
> > @@ -577,7 +585,11 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> > if (cmd == VHOST_SET_BACKEND_FEATURES) {
> > if (copy_from_user(&features, featurep, sizeof(features)))
> > return -EFAULT;
> > - if (features & ~VHOST_VDPA_BACKEND_FEATURES)
> > + if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
> > + BIT_ULL(VHOST_BACKEND_F_SUSPEND)))
> > + return -EOPNOTSUPP;
> > + if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
> > + !vhost_vdpa_can_suspend(v))
>
> Do we need to advertise this to the management?
>

Not sure if I follow, the feature bit is not exposed if the backend
cannot suspend.

Thanks!

> Thanks
>
> > return -EOPNOTSUPP;
> > vhost_set_backend_features(&v->vdev, features);
> > return 0;
> > @@ -628,6 +640,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> > break;
> > case VHOST_GET_BACKEND_FEATURES:
> > features = VHOST_VDPA_BACKEND_FEATURES;
> > + if (vhost_vdpa_can_suspend(v))
> > + features |= BIT_ULL(VHOST_BACKEND_F_SUSPEND);
> > if (copy_to_user(featurep, &features, sizeof(features)))
> > r = -EFAULT;
> > break;
> > diff --git a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> > index 634cee485abb..1bdd6e363f4c 100644
> > --- a/include/uapi/linux/vhost_types.h
> > +++ b/include/uapi/linux/vhost_types.h
> > @@ -161,5 +161,7 @@ struct vhost_vdpa_iova_range {
> > * message
> > */
> > #define VHOST_BACKEND_F_IOTLB_ASID 0x3
> > +/* Device can be suspended */
> > +#define VHOST_BACKEND_F_SUSPEND 0x4
> >
> > #endif
> > --
> > 2.31.1
> >
>

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