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References: <20220623160738.632852-1-eperezma@redhat.com> <20220623160738.632852-3-eperezma@redhat.com>
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From:   Jason Wang <jasowang@redhat.com>
Date:   Wed, 29 Jun 2022 12:12:27 +0800
Message-ID: <CACGkMEtNC=4KeigQXr4NuaiuVGkxK2ruQTk6-Fbr3B1MqHieTA@mail.gmail.com>
Subject: Re: [PATCH v6 2/4] vhost-vdpa: introduce SUSPEND backend feature bit
To:     =?UTF-8?Q?Eugenio_P=C3=A9rez?= <eperezma@redhat.com>
Cc:     netdev <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        virtualization <virtualization@lists.linux-foundation.org>,
        kvm <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>,
        Parav Pandit <parav@nvidia.com>,
        Christophe JAILLET <christophe.jaillet@wanadoo.fr>,
        Cindy Lu <lulu@redhat.com>,
        "Kamde, Tanuj" <tanuj.kamde@amd.com>,
        Si-Wei Liu <si-wei.liu@oracle.com>,
        "Uminski, Piotr" <Piotr.Uminski@intel.com>,
        habetsm.xilinx@gmail.com, "Dawar, Gautam" <gautam.dawar@amd.com>,
        Pablo Cascon Katchadourian <pabloc@xilinx.com>,
        Zhu Lingshan <lingshan.zhu@intel.com>,
        Laurent Vivier <lvivier@redhat.com>,
        Longpeng <longpeng2@huawei.com>,
        Dinan Gunawardena <dinang@xilinx.com>,
        Martin Petrus Hubertus Habets <martinh@xilinx.com>,
        Martin Porter <martinpo@xilinx.com>,
        Eli Cohen <elic@nvidia.com>, ecree.xilinx@gmail.com,
        Wu Zongyong <wuzongyong@linux.alibaba.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Dan Carpenter <dan.carpenter@oracle.com>,
        Harpreet Singh Anand <hanand@xilinx.com>,
        Xie Yongji <xieyongji@bytedance.com>,
        Zhang Min <zhang.min9@zte.com.cn>
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On Fri, Jun 24, 2022 at 12:08 AM Eugenio P=C3=A9rez <eperezma@redhat.com> w=
rote:
>
> Userland knows if it can suspend the device or not by checking this featu=
re
> 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 P=C3=A9rez <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 =3D v->vdpa;
> +       const struct vdpa_config_ops *ops =3D vdpa->config;
> +
> +       return ops->suspend;
> +}
> +
>  static long vhost_vdpa_get_features(struct vhost_vdpa *v, u64 __user *fe=
aturep)
>  {
>         struct vdpa_device *vdpa =3D v->vdpa;
> @@ -577,7 +585,11 @@ static long vhost_vdpa_unlocked_ioctl(struct file *f=
ilep,
>         if (cmd =3D=3D 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 *fi=
lep,
>                 break;
>         case VHOST_GET_BACKEND_FEATURES:
>                 features =3D VHOST_VDPA_BACKEND_FEATURES;
> +               if (vhost_vdpa_can_suspend(v))
> +                       features |=3D BIT_ULL(VHOST_BACKEND_F_SUSPEND);
>                 if (copy_to_user(featurep, &features, sizeof(features)))
>                         r =3D -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
>