Re: [PATCH v7 3/4] vhost-vdpa: uAPI to suspend the device

Michael S. Tsirkin
2022-08-11T08:29:23Z

On Wed, Aug 10, 2022 at 07:15:11PM +0200, Eugenio Pérez wrote:
> The ioctl adds support for suspending the device from userspace.
>
> This is a must before getting virtqueue indexes (base) for live migration,
> since the device could modify them after userland gets them. There are
> individual ways to perform that action for some devices
> (VHOST_NET_SET_BACKEND, VHOST_VSOCK_SET_RUNNING, ...) but there was no
> way to perform it for any vhost device (and, in particular, vhost-vdpa).
>
> After a successful return of the ioctl call the device must not process
> more virtqueue descriptors. The device can answer to read or writes of
> config fields as if it were not suspended. In particular, writing to
> "queue_enable" with a value of 1 will not make the device start
> processing buffers of the virtqueue.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> Message-Id: <20220623160738.632852-4-eperezma@redhat.com>
> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

You are not supposed to include upstream maintainer's signoff
like this.

> ---
> v7: Delete argument to ioctl, unused
> ---
> drivers/vhost/vdpa.c | 19 +++++++++++++++++++
> include/uapi/linux/vhost.h | 9 +++++++++
> 2 files changed, 28 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 3d636e192061..7fa671ac4bdf 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -478,6 +478,22 @@ static long vhost_vdpa_get_vqs_count(struct vhost_vdpa *v, u32 __user *argp)
> return 0;
> }
>
> +/* After a successful return of ioctl the device must not process more
> + * virtqueue descriptors. The device can answer to read or writes of config
> + * fields as if it were not suspended. In particular, writing to "queue_enable"
> + * with a value of 1 will not make the device start processing buffers.
> + */
> +static long vhost_vdpa_suspend(struct vhost_vdpa *v)
> +{
> + struct vdpa_device *vdpa = v->vdpa;
> + const struct vdpa_config_ops *ops = vdpa->config;
> +
> + if (!ops->suspend)
> + return -EOPNOTSUPP;
> +
> + return ops->suspend(vdpa);
> +}
> +
> static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> void __user *argp)
> {
> @@ -654,6 +670,9 @@ static long vhost_vdpa_unlocked_ioctl(struct file *filep,
> case VHOST_VDPA_GET_VQS_COUNT:
> r = vhost_vdpa_get_vqs_count(v, argp);
> break;
> + case VHOST_VDPA_SUSPEND:
> + r = vhost_vdpa_suspend(v);
> + break;
> default:
> r = vhost_dev_ioctl(&v->vdev, cmd, argp);
> if (r == -ENOIOCTLCMD)
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index cab645d4a645..f9f115a7c75b 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -171,4 +171,13 @@
> #define VHOST_VDPA_SET_GROUP_ASID _IOW(VHOST_VIRTIO, 0x7C, \
> struct vhost_vring_state)
>
> +/* Suspend a device so it does not process virtqueue requests anymore
> + *
> + * After the return of ioctl the device must preserve all the necessary state
> + * (the virtqueue vring base plus the possible device specific states) that is
> + * required for restoring in the future. The device must not change its
> + * configuration after that point.
> + */
> +#define VHOST_VDPA_SUSPEND _IO(VHOST_VIRTIO, 0x7D)
> +
> #endif
> --
> 2.31.1