Re: [PATCH] cxl/region: Test CXL_DECODER_F_NORMALIZED_ADDRESSING as a bitmask

[Alison Schofield <alison.schofield@intel.com>]

On Thu, Feb 05, 2026 at 05:31:33PM -0800, Alison Schofield wrote:
> CXL_DECODER_F_NORMALIZED_ADDRESSING is a bitmask, not a bit index.
> Using test_bit() to check it caused undefined behavior making the
> flag sometimes appear set. This prevented creation of CXL region
> debugfs attributes that support poison actions.
> 
> Replace test_bit() with a bitmask check.
> 
> Found with cxl-test.

I was focused on getting this test case to work so it wasn't
until I hit send on the patch that I see there are a couple of
other places to stop using test_bit().
I'll respin and clean these up too:

hdm.c:		if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags))
region.c:	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags)) {

> 
> Fixes: 208f432406b7 ("cxl: Disable HPA/SPA translation handlers for Normalized Addressing")
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
> 
> DaveJ: The base commit tag is linux-next today. I figure it's closest to what
> we'll see w 7.0-rc1. 
> 
> 
>  drivers/cxl/core/region.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 08fa3deef70a..00a9b57cdd80 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1105,7 +1105,7 @@ static void cxl_region_setup_flags(struct cxl_region *cxlr,
>  		clear_bit(CXL_REGION_F_NEEDS_RESET, &cxlr->flags);
>  	}
>  
> -	if (test_bit(CXL_DECODER_F_NORMALIZED_ADDRESSING, &cxld->flags))
> +	if (cxld->flags & CXL_DECODER_F_NORMALIZED_ADDRESSING)
>  		set_bit(CXL_REGION_F_NORMALIZED_ADDRESSING, &cxlr->flags);
>  }
>  
> 
> base-commit: 9845cf73f7db6094c0d8419d6adb848028f4a921
> -- 
> 2.37.3
>