[Devel] [PATCH RH9 v2 06/10] drivers/vhost: add ioctl to increase the number of workers

[Andrey Zhadchenko]

On 9/8/22 18:32, Andrey Zhadchenko wrote:
> Finally add ioctl to allow userspace to create additional workers
> For now only allow to increase the number of workers
> 
> https://jira.sw.ru/browse/PSBM-139414
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
> ---
> v2:
>   - Make code do what docs suggest. Previously ioctl-supplied new number
> of workers were treated like an amount that should be added. Use new
> number as a ceiling instead and add workers up to that number.
> 
>   drivers/vhost/vhost.c      | 32 +++++++++++++++++++++++++++++++-
>   include/uapi/linux/vhost.h |  9 +++++++++
>   2 files changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 0542eab1e815..9066241e8dc6 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -656,6 +656,25 @@ static int vhost_add_worker(struct vhost_dev *dev)
>   	return err;
>   }
>   
> +static int vhost_set_workers(struct vhost_dev *dev, int n)
> +{
> +	int i, ret;
> +
> +	if (n > dev->nvqs)
> +		n = dev->nvqs;
> +
> +	if (n > VHOST_MAX_WORKERS)
> +		n = VHOST_MAX_WORKERS;
> +
> +	for (i = 0; i < n - dev->nworkers ; i++) {
> +		ret = vhost_add_worker(dev);
> +		if (ret)
> +			break;
> +	}
> +
> +	return ret;
> +}
> +
>   /* Caller should have device mutex */
>   long vhost_dev_set_owner(struct vhost_dev *dev)
>   {
> @@ -1809,7 +1828,7 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
>   	struct eventfd_ctx *ctx;
>   	u64 p;
>   	long r;
> -	int i, fd;
> +	int i, fd, n;
>   
>   	/* If you are not the owner, you can become one */
>   	if (ioctl == VHOST_SET_OWNER) {
> @@ -1866,6 +1885,17 @@ long vhost_dev_ioctl(struct vhost_dev *d, unsigned int ioctl, void __user *argp)
>   		if (ctx)
>   			eventfd_ctx_put(ctx);
>   		break;
> +	case VHOST_SET_NWORKERS:
> +		r = get_user(n, (int __user *)argp);
> +		if (r < 0)
> +			break;
> +		if (n < d->nworkers) {
> +			r = -EINVAL;
> +			break;
> +		}
> +
> +		r = vhost_set_workers(d, n);
> +		break;
>   	default:
>   		r = -ENOIOCTLCMD;
>   		break;
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 13caf114bcde..d6d87f6315f6 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -71,6 +71,15 @@
>   #define VHOST_SET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x13, struct vhost_vring_state)
>   #define VHOST_GET_VRING_ENDIAN _IOW(VHOST_VIRTIO, 0x14, struct vhost_vring_state)
>   
> +/* Set number of vhost workers
> + * Currently nuber of vhost workers can only be increased.
typo. should be "number" - will be fixed in next patches
> + * All workers are freed upon reset.
> + * If the value is too big it is silently truncated to the maximum number of
> + * supported vhost workers
> + * Even if the error is returned it is possible that some workers were created
> + */
> +#define VHOST_SET_NWORKERS _IOW(VHOST_VIRTIO, 0x1F, int)
> +
>   /* The following ioctls use eventfd file descriptors to signal and poll
>    * for events. */
>