Re: [PATCH] vfio: unhide vdev->debug_root

[Alex Williamson <alex@shazbot.org>]

On Fri, 27 Mar 2026 17:55:08 +0100
Arnd Bergmann <arnd@kernel.org> wrote:

> From: Arnd Bergmann <arnd@arndb.de>
> 
> When debugfs is disabled, the hisilicon driver now fails to build:
> 
> drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c: In function 'hisi_acc_vfio_debug_init':
> drivers/vfio/pci/hisilicon/hisi_acc_vfio_pci.c:1671:62: error: 'struct vfio_device' has no member named 'debug_root'
>  1671 |         vfio_dev_migration = debugfs_lookup("migration", vdev->debug_root);
>       |                                                              ^~
> 
> The driver otherwise relies on dead-code elimination, but this reference
> fails. The single struct member is not going to make much of a difference
> for memory consumption, so just keep this visible unconditionally.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ----
> This seems to be a new build failure, but I could not pinpoint which
> commit caused it, as both the #ifdef and the the use were introduced
> a while ago.
> ---

They were introduced some time apart, but I'd attribute it to the use
here in the hisi_acc driver, ie. Fixes: b398f91779b8
("hisi_acc_vfio_pci: register debugfs for hisilicon migration driver").
The series introducing debug_root had proper stubs to avoid references.

I'll add that on commit, otherwise LGTM.  Thanks,

Alex


>  include/linux/vfio.h | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index 50b474334a19..31b826efba00 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -74,13 +74,11 @@ struct vfio_device {
>  	u8 iommufd_attached:1;
>  #endif
>  	u8 cdev_opened:1;
> -#ifdef CONFIG_DEBUG_FS
>  	/*
>  	 * debug_root is a static property of the vfio_device
>  	 * which must be set prior to registering the vfio_device.
>  	 */
>  	struct dentry *debug_root;
> -#endif
>  };
>  
>  /**