On Wed, Aug 16, 2023 at 7:54 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
>
>
>
> On 8/9/2023 8:49 PM, Jason Wang wrote:
> > On Wed, Aug 9, 2023 at 8:56 PM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
> >> Userspace knows if the device has dedicated descriptor group or not
> >> by checking this feature bit.
> >>
> >> It's only exposed if the vdpa driver backend implements the
> >> .get_vq_desc_group() operation callback. Userspace trying to negotiate
> >> this feature when it or the dependent _F_IOTLB_ASID feature hasn't
> >> been exposed will result in an error.
> >>
> >> Signed-off-by: Si-Wei Liu <si-wei.liu@xxxxxxxxxx>
> >> ---
> >> drivers/vhost/vdpa.c | 17 +++++++++++++++++
> >> include/uapi/linux/vhost_types.h | 5 +++++
> >> 2 files changed, 22 insertions(+)
> >>
> >> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> >> index b43e868..f2e5dce 100644
> >> --- a/drivers/vhost/vdpa.c
> >> +++ b/drivers/vhost/vdpa.c
> >> @@ -389,6 +389,14 @@ static bool vhost_vdpa_can_resume(const struct vhost_vdpa *v)
> >> return ops->resume;
> >> }
> >>
> >> +static bool vhost_vdpa_has_desc_group(const struct vhost_vdpa *v)
> >> +{
> >> + struct vdpa_device *vdpa = v->vdpa;
> >> + const struct vdpa_config_ops *ops = vdpa->config;
> >> +
> >> + return ops->get_vq_desc_group;
> >> +}
> >> +
> >> static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *featurep)
> >> {
> >> struct vdpa_device *vdpa = v->vdpa;
> >> @@ -679,6 +687,7 @@ 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_DESC_ASID) |
> >> BIT_ULL(VHOST_BACKEND_F_SUSPEND) |
> >> BIT_ULL(VHOST_BACKEND_F_RESUME)))
> >> return -EOPNOTSUPP;
> >> @@ -688,6 +697,12 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> >> if ((features & BIT_ULL(VHOST_BACKEND_F_RESUME)) &&
> >> !vhost_vdpa_can_resume(v))
> >> return -EOPNOTSUPP;
> >> + if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
> >> + !(features & BIT_ULL(VHOST_BACKEND_F_IOTLB_ASID)))
> >> + return -EINVAL;
> >> + if ((features & BIT_ULL(VHOST_BACKEND_F_DESC_ASID)) &&
> >> + !vhost_vdpa_has_desc_group(v))
> >> + return -EOPNOTSUPP;
> >> vhost_set_backend_features(&v->vdev, features);
> >> return 0;
> >> }
> >> @@ -741,6 +756,8 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> >> features |= BIT_ULL(VHOST_BACKEND_F_SUSPEND);
> >> if (vhost_vdpa_can_resume(v))
> >> features |= BIT_ULL(VHOST_BACKEND_F_RESUME);
> >> + if (vhost_vdpa_has_desc_group(v))
> >> + features |= BIT_ULL(VHOST_BACKEND_F_DESC_ASID);
> >> 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 d3aad12a..0856f84 100644
> >> --- a/include/uapi/linux/vhost_types.h
> >> +++ b/include/uapi/linux/vhost_types.h
> >> @@ -181,5 +181,10 @@ struct vhost_vdpa_iova_range {
> >> #define VHOST_BACKEND_F_SUSPEND 0x4
> >> /* Device can be resumed */
> >> #define VHOST_BACKEND_F_RESUME 0x5
> >> +/* Device may expose the descriptor table, avail and used ring in a
> >> + * different group for ASID binding than the buffers it contains.
> > Nit:
> >
> > s/a different group/different groups/?
> Yep, I will try to rephrase. Would below work?
>
> "Device may expose virtqueue's descriptor table, avail and used ring in a
> different group for ASID binding than where buffers it contains reside."
>
> > Btw, not a native speaker but I think "descriptor" might be confusing
> > since as you explained above, it contains more than just a descriptor
> > table.
> Yep. I chose "descriptor" because packed virtqueue doesn't have
> "physical" avail and used ring other than descriptor table, but I think
> I am open to a better name. I once thought of "descriptor ring" but that
> might be too specific to packed virtqueue. Any suggestion?
I don't have a better idea, probably "metadata" ?
Thanks
>
> Thanks,
> -Siwei
>
> >
> > Thanks
> >
> >> + * Requires VHOST_BACKEND_F_IOTLB_ASID.
> >> + */
> >> +#define VHOST_BACKEND_F_DESC_ASID 0x6
> >>
> >> #endif
> >> --
> >> 1.8.3.1
> >>
>
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