On Fri, Oct 14, 2022 at 02:09:02PM +0800, Jason Wang wrote:
> On Fri, Oct 14, 2022 at 2:05 PM Michael S. Tsirkin <[email protected]> wrote:
> >
> > On Fri, Oct 14, 2022 at 01:58:38PM +0800, Jason Wang wrote:
> > > On Thu, Oct 13, 2022 at 11:35 PM <[email protected]> wrote:
> > > >
> > > > From: Sebastien Boeuf <[email protected]>
> > > >
> > > > Userspace knows if the device can be resumed or not by checking this
> > > > feature bit.
> > > >
> > > > It's only exposed if the vdpa driver backend implements the resume()
> > > > operation callback. Userspace trying to negotiate this feature when it
> > > > hasn't been exposed will result in an error.
> > > >
> > > > Signed-off-by: Sebastien Boeuf <[email protected]>
> > > > ---
> > > > drivers/vhost/vdpa.c | 19 ++++++++++++++++++-
> > > > include/uapi/linux/vhost_types.h | 2 ++
> > > > 2 files changed, 20 insertions(+), 1 deletion(-)
> > > >
> > > > diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> > > > index 166044642fd5..161727e1a9a5 100644
> > > > --- a/drivers/vhost/vdpa.c
> > > > +++ b/drivers/vhost/vdpa.c
> > > > @@ -355,6 +355,14 @@ static bool vhost_vdpa_can_suspend(const struct
> > > > vhost_vdpa *v)
> > > > return ops->suspend;
> > > > }
> > > >
> > > > +static bool vhost_vdpa_can_resume(const struct vhost_vdpa *v)
> > > > +{
> > > > + struct vdpa_device *vdpa = v->vdpa;
> > > > + const struct vdpa_config_ops *ops = vdpa->config;
> > > > +
> > > > + return ops->resume;
> > > > +}
> > > > +
> > > > static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user
> > > > *featurep)
> > > > {
> > > > struct vdpa_device *vdpa = v->vdpa;
> > > > @@ -602,11 +610,18 @@ static long vhost_vdpa_unlocked_ioctl(struct file
> > > > *filep,
> > > > if (copy_from_user(&features, featurep,
> > > > sizeof(features)))
> > > > return -EFAULT;
> > > > if (features & ~(VHOST_VDPA_BACKEND_FEATURES |
> > > > - BIT_ULL(VHOST_BACKEND_F_SUSPEND)))
> > > > + BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
> > > > + BIT_ULL(VHOST_BACKEND_F_RESUME)))
> > > > return -EOPNOTSUPP;
> > > > if ((features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
> > > > !vhost_vdpa_can_suspend(v))
> > > > return -EOPNOTSUPP;
> > > > + if ((features & BIT_ULL(VHOST_BACKEND_F_RESUME)) &&
> > > > + !vhost_vdpa_can_resume(v))
> > > > + return -EOPNOTSUPP;
> > > > + if (!(features & BIT_ULL(VHOST_BACKEND_F_SUSPEND)) &&
> > > > + (features & BIT_ULL(VHOST_BACKEND_F_RESUME)))
> > > > + return -EINVAL;
> > >
> > > Is it better to do the check during the probe? It should be a bug that
> > > we're having a parent that can only do resume but not suspend.
> > >
> > > Thanks
> >
> > well we separated them in the spec ...
> > suspend could have other uses, I won't say it's an invalid
> > config.
>
> For suspend only, yes. But we should fail the probe with a resume
> only, this is somehow the above code wants to check. Or anything I
> missed?
>
> Thanks
I am not sure but I would say failing probe is a drastic measure.
if we have no use for a given combination of features let us clear the
feature bit in validation.
> >
> > > > vhost_set_backend_features(&v->vdev, features);
> > > > return 0;
> > > > }
> > > > @@ -658,6 +673,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file
> > > > *filep,
> > > > features = VHOST_VDPA_BACKEND_FEATURES;
> > > > if (vhost_vdpa_can_suspend(v))
> > > > features |= BIT_ULL(VHOST_BACKEND_F_SUSPEND);
> > > > + if (vhost_vdpa_can_resume(v))
> > > > + features |= BIT_ULL(VHOST_BACKEND_F_RESUME);
> > > > 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 53601ce2c20a..c5690a8992d8 100644
> > > > --- a/include/uapi/linux/vhost_types.h
> > > > +++ b/include/uapi/linux/vhost_types.h
> > > > @@ -163,5 +163,7 @@ struct vhost_vdpa_iova_range {
> > > > #define VHOST_BACKEND_F_IOTLB_ASID 0x3
> > > > /* Device can be suspended */
> > > > #define VHOST_BACKEND_F_SUSPEND 0x4
> > > > +/* Device can be resumed */
> > > > +#define VHOST_BACKEND_F_RESUME 0x5
> > > >
> > > > #endif
> > > > --
> > > > 2.34.1
> > > >
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