Re: [PATCH] vfio/cdx: Add parentheses between bitwise AND expression and logical NOT

[Alex Williamson <alex.williamson@redhat.com>]

On Mon, 02 Oct 2023 10:53:13 -0700
Nathan Chancellor <nathan@kernel.org> wrote:

> When building with clang, there is a warning (or error with
> CONFIG_WERROR=y) due to a bitwise AND and logical NOT in
> vfio_cdx_bm_ctrl():
> 
>   drivers/vfio/cdx/main.c:77:6: error: logical not is only applied to the left hand side of this bitwise operator [-Werror,-Wlogical-not-parentheses]
>      77 |         if (!vdev->flags & BME_SUPPORT)
>         |             ^            ~
>   drivers/vfio/cdx/main.c:77:6: note: add parentheses after the '!' to evaluate the bitwise operator first
>      77 |         if (!vdev->flags & BME_SUPPORT)
>         |             ^
>         |              (                        )
>   drivers/vfio/cdx/main.c:77:6: note: add parentheses around left hand side expression to silence this warning
>      77 |         if (!vdev->flags & BME_SUPPORT)
>         |             ^
>         |             (           )
>   1 error generated.
> 
> Add the parentheses as suggested in the first note, which is clearly
> what was intended here.
> 
> Closes: https://github.com/ClangBuiltLinux/linux/issues/1939
> Fixes: 8a97ab9b8b31 ("vfio-cdx: add bus mastering device feature support")
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>  drivers/vfio/cdx/main.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vfio/cdx/main.c b/drivers/vfio/cdx/main.c
> index a437630be354..a63744302b5e 100644
> --- a/drivers/vfio/cdx/main.c
> +++ b/drivers/vfio/cdx/main.c
> @@ -74,7 +74,7 @@ static int vfio_cdx_bm_ctrl(struct vfio_device *core_vdev, u32 flags,
>  	struct vfio_device_feature_bus_master ops;
>  	int ret;
>  
> -	if (!vdev->flags & BME_SUPPORT)
> +	if (!(vdev->flags & BME_SUPPORT))
>  		return -ENOTTY;
>  
>  	ret = vfio_check_feature(flags, argsz, VFIO_DEVICE_FEATURE_SET,
> 
> ---
> base-commit: fcb2f2ed4a80cfe383d87da75caba958516507e9
> change-id: 20231002-vfio-cdx-logical-not-parentheses-aca8fbd6b278
> 
> Best regards,

Applied to vfio next branch for v6.7.  Thanks!

Alex