[PATCH] cxl: Test decoder flags as bitmasks

[PATCH] cxl: Test decoder flags as bitmasks

[Alison Schofield]

The CXL decoder flags are defined as bitmasks, not bit indices.
Using test_bit() to check them interprets the mask value as a bit
index, which is the wrong test.

For CXL_DECODER_F_NORMALIZED_ADDRESSING the test reads beyond the
flags word, making the flag sometimes appear set and blocking creation
of CXL region debugfs attributes that support poison operations.

For CXL_DECODER_F_LOCK the test reads beyond the defined bits, causing
the test to always return false and allowing resets that should have
been blocked.

Replace test_bit() with a bitmask check.

Found with cxl-test.

Fixes: 208f432406b7 ("cxl: Disable HPA/SPA translation handlers for Normalized Addressing")
Fixes: 2230c4bdc412 ("cxl: Add handling of locked CXL decoder")
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
---

Obsoletes prior patch that only fixed up one test:
cxl/region: Test CXL_DECODER_F_NORMALIZED_ADDRESSING as a bitmask
https://lore.kernel.org/linux-cxl/20260206013135.1012375-1-alison.schofield@intel.com/


 drivers/cxl/core/hdm.c    | 2 +-
 drivers/cxl/core/region.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
index e3f0c39e6812..c222e98ae736 100644
--- a/drivers/cxl/core/hdm.c
+++ b/drivers/cxl/core/hdm.c
@@ -904,7 +904,7 @@ static void cxl_decoder_reset(struct cxl_decoder *cxld)
 	if ((cxld->flags & CXL_DECODER_F_ENABLE) == 0)
 		return;
 
-	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags))
+	if (cxld->flags & CXL_DECODER_F_LOCK)
 		return;
 
 	if (port->commit_end == id)
diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
index 08fa3deef70a..befa2a7b81c2 100644
--- a/drivers/cxl/core/region.c
+++ b/drivers/cxl/core/region.c
@@ -1100,12 +1100,12 @@ static int cxl_rr_assign_decoder(struct cxl_port *port, struct cxl_region *cxlr,
 static void cxl_region_setup_flags(struct cxl_region *cxlr,
 				   struct cxl_decoder *cxld)
 {
-	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags)) {
+	if (cxld->flags & CXL_DECODER_F_LOCK) {
 		set_bit(CXL_REGION_F_LOCK, &cxlr->flags);
 		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

Re: [PATCH] cxl: Test decoder flags as bitmasks

[Dave Jiang]

On 2/6/26 11:14 AM, Alison Schofield wrote:
> The CXL decoder flags are defined as bitmasks, not bit indices.
> Using test_bit() to check them interprets the mask value as a bit
> index, which is the wrong test.
> 
> For CXL_DECODER_F_NORMALIZED_ADDRESSING the test reads beyond the
> flags word, making the flag sometimes appear set and blocking creation
> of CXL region debugfs attributes that support poison operations.
> 
> For CXL_DECODER_F_LOCK the test reads beyond the defined bits, causing
> the test to always return false and allowing resets that should have
> been blocked.
> 
> Replace test_bit() with a bitmask check.
> 
> Found with cxl-test.
> 
> Fixes: 208f432406b7 ("cxl: Disable HPA/SPA translation handlers for Normalized Addressing")
> Fixes: 2230c4bdc412 ("cxl: Add handling of locked CXL decoder")

Given it needs to back port and fix 2 different commits, maybe this needs to split?

> Signed-off-by: Alison Schofield <alison.schofield@intel.com>
> ---
> 
> Obsoletes prior patch that only fixed up one test:
> cxl/region: Test CXL_DECODER_F_NORMALIZED_ADDRESSING as a bitmask
> https://lore.kernel.org/linux-cxl/20260206013135.1012375-1-alison.schofield@intel.com/
> 
> 
>  drivers/cxl/core/hdm.c    | 2 +-
>  drivers/cxl/core/region.c | 4 ++--
>  2 files changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
> index e3f0c39e6812..c222e98ae736 100644
> --- a/drivers/cxl/core/hdm.c
> +++ b/drivers/cxl/core/hdm.c
> @@ -904,7 +904,7 @@ static void cxl_decoder_reset(struct cxl_decoder *cxld)
>  	if ((cxld->flags & CXL_DECODER_F_ENABLE) == 0)
>  		return;
>  
> -	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags))
> +	if (cxld->flags & CXL_DECODER_F_LOCK)
>  		return;
>  
>  	if (port->commit_end == id)
> diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c
> index 08fa3deef70a..befa2a7b81c2 100644
> --- a/drivers/cxl/core/region.c
> +++ b/drivers/cxl/core/region.c
> @@ -1100,12 +1100,12 @@ static int cxl_rr_assign_decoder(struct cxl_port *port, struct cxl_region *cxlr,
>  static void cxl_region_setup_flags(struct cxl_region *cxlr,
>  				   struct cxl_decoder *cxld)
>  {
> -	if (test_bit(CXL_DECODER_F_LOCK, &cxld->flags)) {
> +	if (cxld->flags & CXL_DECODER_F_LOCK) {
>  		set_bit(CXL_REGION_F_LOCK, &cxlr->flags);
>  		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

Re: [PATCH] cxl: Test decoder flags as bitmasks

[Alison Schofield]

On Fri, Feb 06, 2026 at 12:33:34PM -0700, Dave Jiang wrote:
> 
> 
> On 2/6/26 11:14 AM, Alison Schofield wrote:
> > The CXL decoder flags are defined as bitmasks, not bit indices.
> > Using test_bit() to check them interprets the mask value as a bit
> > index, which is the wrong test.
> > 
> > For CXL_DECODER_F_NORMALIZED_ADDRESSING the test reads beyond the
> > flags word, making the flag sometimes appear set and blocking creation
> > of CXL region debugfs attributes that support poison operations.
> > 
> > For CXL_DECODER_F_LOCK the test reads beyond the defined bits, causing
> > the test to always return false and allowing resets that should have
> > been blocked.
> > 
> > Replace test_bit() with a bitmask check.
> > 
> > Found with cxl-test.
> > 
> > Fixes: 208f432406b7 ("cxl: Disable HPA/SPA translation handlers for Normalized Addressing")
> > Fixes: 2230c4bdc412 ("cxl: Add handling of locked CXL decoder")
> 
> Given it needs to back port and fix 2 different commits, maybe this needs to split?

OK - will do, ignore this patch.

It'll be a 2 patch series because of the dependency, but I believe that
is still preferred by backport folks.

Re: [PATCH] cxl: Test decoder flags as bitmasks

[Davidlohr Bueso]

On Fri, 06 Feb 2026, Alison Schofield wrote:

>The CXL decoder flags are defined as bitmasks, not bit indices.
>Using test_bit() to check them interprets the mask value as a bit
>index, which is the wrong test.
>
>For CXL_DECODER_F_NORMALIZED_ADDRESSING the test reads beyond the
>flags word, making the flag sometimes appear set and blocking creation
>of CXL region debugfs attributes that support poison operations.
>
>For CXL_DECODER_F_LOCK the test reads beyond the defined bits, causing
>the test to always return false and allowing resets that should have
>been blocked.
>
>Replace test_bit() with a bitmask check.
>
>Found with cxl-test.
>

Nice find. Other than splitting the fixes as suggested by Dave:

Reviewed-by: Davidlohr Bueso <dave@stgolabs.net>

Re: [PATCH] cxl: Test decoder flags as bitmasks

[Gregory Price]

On Fri, Feb 06, 2026 at 10:14:02AM -0800, Alison Schofield wrote:
> The CXL decoder flags are defined as bitmasks, not bit indices.
> Using test_bit() to check them interprets the mask value as a bit
> index, which is the wrong test.
> 
> For CXL_DECODER_F_NORMALIZED_ADDRESSING the test reads beyond the
> flags word, making the flag sometimes appear set and blocking creation
> of CXL region debugfs attributes that support poison operations.
> 
> For CXL_DECODER_F_LOCK the test reads beyond the defined bits, causing
> the test to always return false and allowing resets that should have
> been blocked.
> 
> Replace test_bit() with a bitmask check.
> 
> Found with cxl-test.
> 
> Fixes: 208f432406b7 ("cxl: Disable HPA/SPA translation handlers for Normalized Addressing")
> Fixes: 2230c4bdc412 ("cxl: Add handling of locked CXL decoder")
> Signed-off-by: Alison Schofield <alison.schofield@intel.com>

I independently found and fixed this with the same patch.  So +1

Reviewed-by: Gregory Price <gourry@gourry.net>
Tested-by: Gregory Price <gourry@gourry.net>