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/?
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.
Thanks
> + * Requires VHOST_BACKEND_F_IOTLB_ASID.
> + */
> +#define VHOST_BACKEND_F_DESC_ASID 0x6
>
> #endif
> --
> 1.8.3.1
>
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