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SubjectRe: [PATCH v6 2/4] vhost-vdpa: introduce SUSPEND backend feature bit
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?

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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