Re: [BUG] vhost: perf tools build error after syncing vhost.h

[Arnaldo Carvalho de Melo <acme@kernel.org>]

On Mon, Aug 18, 2025 at 01:23:10PM -0700, Namhyung Kim wrote:
> Hello,
> 
> I was sync'ing perf tools copy of kernel sources to apply recent
> changes.  But there's a build error when it converts vhost ioctl
> commands due to a conflicting slot like below.

I haven't looked at this specific case in detail, but in the past the
synchronization of tools/ copies did catch things like this, yes :-)

- Arnaldo
 
>   In file included from trace/beauty/ioctl.c:93:
>   tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c: In function ‘ioctl__scnprintf_vhost_virtio_cmd’:
>   tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: error: initialized field overwritten [-Werror=override-init]
>      36 |         [0x83] = "SET_FORK_FROM_OWNER",
>         |                  ^~~~~~~~~~~~~~~~~~~~~
>   tools/perf/trace/beauty/generated/ioctl/vhost_virtio_ioctl_array.c:36:18: note: (near initialization for ‘vhost_virtio_ioctl_cmds[131]’)
>   
> I think the following changes both added entries to 0x83.
> 
>   7d9896e9f6d02d8a vhost: Reintroduce kthread API and add mode selection
>   333c515d189657c9 vhost-net: allow configuring extended features
> 
> The below patch fixes it for me.
> 
> Thanks,
> Namhyung
> 
> 
> ---8<---
> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
> index 283348b64af9ac59..c57674a6aa0dbbea 100644
> --- a/include/uapi/linux/vhost.h
> +++ b/include/uapi/linux/vhost.h
> @@ -260,7 +260,7 @@
>   * When fork_owner is set to VHOST_FORK_OWNER_KTHREAD:
>   *   - Vhost will create vhost workers as kernel threads.
>   */
> -#define VHOST_SET_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x83, __u8)
> +#define VHOST_SET_FORK_FROM_OWNER _IOW(VHOST_VIRTIO, 0x84, __u8)
>  
>  /**
>   * VHOST_GET_FORK_OWNER - Get the current fork_owner flag for the vhost device.
> @@ -268,6 +268,6 @@
>   *
>   * @return: An 8-bit value indicating the current thread mode.
>   */
> -#define VHOST_GET_FORK_FROM_OWNER _IOR(VHOST_VIRTIO, 0x84, __u8)
> +#define VHOST_GET_FORK_FROM_OWNER _IOR(VHOST_VIRTIO, 0x85, __u8)
>  
>  #endif