Re: [PATCH v4 3/4] vhost-vdpa: uAPI to stop the device

Michael S. Tsirkin
2022-06-01T11:04:00Z

On Thu, May 26, 2022 at 02:43:37PM +0200, Eugenio Pérez wrote:
> The ioctl adds support for stop the device from userspace.
>
> Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
> ---
> drivers/vhost/vdpa.c | 18 ++++++++++++++++++
> include/uapi/linux/vhost.h | 14 ++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 32713db5831d..d1d19555c4b7 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -478,6 +478,21 @@ static long vhost_vdpa_get_vqs_count(struct vhost_vdpa *v, u32 __user *argp)
> return 0;
> }
>
> +static long vhost_vdpa_stop(struct vhost_vdpa *v, u32 __user *argp)
> +{
> + struct vdpa_device *vdpa = v->vdpa;
> + const struct vdpa_config_ops *ops = vdpa->config;
> + int stop;
> +
> + if (!ops->stop)
> + return -EOPNOTSUPP;
> +
> + if (copy_from_user(&stop, argp, sizeof(stop)))
> + return -EFAULT;
> +
> + return ops->stop(vdpa, stop);
> +}
> +
> static long vhost_vdpa_vring_ioctl(struct vhost_vdpa *v, unsigned int cmd,
> void __user *argp)
> {
> @@ -650,6 +665,9 @@ 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_STOP:
> + r = vhost_vdpa_stop(v, argp);
> + 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..c7e47b29bf61 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -171,4 +171,18 @@
> #define VHOST_VDPA_SET_GROUP_ASID _IOW(VHOST_VIRTIO, 0x7C, \
> struct vhost_vring_state)
>
> +/* Stop or resume a device so it does not process virtqueue requests anymore
> + *
> + * After the return of ioctl with stop != 0, the device must finish any
> + * pending operations like in flight requests. It must also 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.
> + *
> + * After the return of ioctl with stop == 0, the device can continue
> + * processing buffers as long as typical conditions are met (vq is enabled,
> + * DRIVER_OK status bit is enabled, etc).
> + */
> +#define VHOST_VDPA_STOP _IOW(VHOST_VIRTIO, 0x7D, int)
> +
> #endif

I wonder how does this interact with the admin vq idea.
I.e. if we stop all VQs then apparently admin vq can't
work either ...
Thoughts?

> --
> 2.31.1