[PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Dan Williams]

git bisect flags:

6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")

...as the reason basic CXL unit tests are failing on latest mainline. In
addition to the fix to einj-core.c, this also needs some updates to
faux_device to make it behave more like platform_driver_probe(). Details
in the individual patches.

Dan Williams (3):
  driver core: faux: Suppress bind attributes
  driver core: faux: Quiet probe failures
  ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create()
    failure

 drivers/acpi/apei/einj-core.c | 9 +++------
 drivers/base/faux.c           | 3 ++-
 2 files changed, 5 insertions(+), 7 deletions(-)


base-commit: a9dfb7db96f7bc1f30feae673aab7fdbfbc94e9c
-- 
2.49.0

[PATCH 1/3] driver core: faux: Suppress bind attributes

[Dan Williams]

faux_device_create() is almost a suitable candidate to replace
platform_driver_probe() if not for the fact that faux_device_create()
supports dynamic attach/detach of the driver.

Drop the bind attributes with the expectation that simple faux devices can
always assume that the device is permanently bound at create, and only
unbound at 'destroy'.

The acpi-einj driver depends on static bind.

Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/base/faux.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/base/faux.c b/drivers/base/faux.c
index 9054d346bd7f..934da77ca48b 100644
--- a/drivers/base/faux.c
+++ b/drivers/base/faux.c
@@ -86,6 +86,7 @@ static struct device_driver faux_driver = {
 	.name		= "faux_driver",
 	.bus		= &faux_bus_type,
 	.probe_type	= PROBE_FORCE_SYNCHRONOUS,
+	.suppress_bind_attrs = true,
 };
 
 static void faux_device_release(struct device *dev)
-- 
2.49.0

[PATCH 2/3] driver core: faux: Quiet probe failures

[Dan Williams]

The acpi-einj conversion to faux_device_create() leads to a noisy error
message when the error injection facility is disabled. Quiet the error as
CXL error injection via ACPI expects the module to stay loaded even if the
error injection facility is disabled.

This situation arose because CXL knows proper kernel named objects to
trigger errors against, but acpi-einj knows how to perform the error
injection. The injection mechanism is shared with non-CXL use cases. The
result is CXL now has a module dependency on einj-core.ko, and init/probe
failures are handled at runtime.

Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/base/faux.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/base/faux.c b/drivers/base/faux.c
index 934da77ca48b..f5fbda0a9a44 100644
--- a/drivers/base/faux.c
+++ b/drivers/base/faux.c
@@ -170,7 +170,7 @@ struct faux_device *faux_device_create_with_groups(const char *name,
 	 * successful is almost impossible to determine by the caller.
 	 */
 	if (!dev->driver) {
-		dev_err(dev, "probe did not succeed, tearing down the device\n");
+		dev_dbg(dev, "probe did not succeed, tearing down the device\n");
 		faux_device_destroy(faux_dev);
 		faux_dev = NULL;
 	}
-- 
2.49.0

[PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Dan Williams]

CXL has a symbol dependency on einj_core.ko, so if einj_init() fails then
cxl_core.ko fails to load. Prior to the faux_device_create() conversion,
einj_probe() failures were tracked by the einj_initialized flag without
failing einj_init().

Revert to that behavior and always succeed einj_init() given there is no
way, and no pressing need, to discern faux device-create vs device-probe
failures.

This situation arose because CXL knows proper kernel named objects to
trigger errors against, but acpi-einj knows how to perform the error
injection. The injection mechanism is shared with non-CXL use cases. The
result is CXL now has a module dependency on einj-core.ko, and init/probe
failures are handled at runtime.

Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Sudeep Holla <sudeep.holla@arm.com>
Cc: Ben Cheatham <Benjamin.Cheatham@amd.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/acpi/apei/einj-core.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
index fea11a35eea3..9b041415a9d0 100644
--- a/drivers/acpi/apei/einj-core.c
+++ b/drivers/acpi/apei/einj-core.c
@@ -883,19 +883,16 @@ static int __init einj_init(void)
 	}
 
 	einj_dev = faux_device_create("acpi-einj", NULL, &einj_device_ops);
-	if (!einj_dev)
-		return -ENODEV;
 
-	einj_initialized = true;
+	if (einj_dev)
+		einj_initialized = true;
 
 	return 0;
 }
 
 static void __exit einj_exit(void)
 {
-	if (einj_initialized)
-		faux_device_destroy(einj_dev);
-
+	faux_device_destroy(einj_dev);
 }
 
 module_init(einj_init);
-- 
2.49.0

Re: [PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Jonathan Cameron]

On Fri, 6 Jun 2025 20:32:28 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> CXL has a symbol dependency on einj_core.ko, so if einj_init() fails then
> cxl_core.ko fails to load. Prior to the faux_device_create() conversion,
> einj_probe() failures were tracked by the einj_initialized flag without
> failing einj_init().
> 
> Revert to that behavior and always succeed einj_init() given there is no
> way, and no pressing need, to discern faux device-create vs device-probe
> failures.
> 
> This situation arose because CXL knows proper kernel named objects to
> trigger errors against, but acpi-einj knows how to perform the error
> injection. The injection mechanism is shared with non-CXL use cases. The
> result is CXL now has a module dependency on einj-core.ko, and init/probe
> failures are handled at runtime.
> 
> Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Cc: Ben Cheatham <Benjamin.Cheatham@amd.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/acpi/apei/einj-core.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
> index fea11a35eea3..9b041415a9d0 100644
> --- a/drivers/acpi/apei/einj-core.c
> +++ b/drivers/acpi/apei/einj-core.c
> @@ -883,19 +883,16 @@ static int __init einj_init(void)
>  	}
>  
>  	einj_dev = faux_device_create("acpi-einj", NULL, &einj_device_ops);
> -	if (!einj_dev)
> -		return -ENODEV;
>  
> -	einj_initialized = true;
> +	if (einj_dev)
> +		einj_initialized = true;
>  
>  	return 0;
>  }
>  
>  static void __exit einj_exit(void)
>  {
> -	if (einj_initialized)
> -		faux_device_destroy(einj_dev);
> -
> +	faux_device_destroy(einj_dev);

Hi Dan,

Thi bit is sort of fine though not really related, because
faux_device_destroy() checks

void faux_device_destroy(struct faux_device *faux_dev)
{
	struct device *dev = &faux_dev->dev;

	if (!faux_dev)
		return;

Though that check is after a dereference of faux_dev
which doesn't look right to me.  Might be fine because
of how the kernel is built (I can't remember where we ended
up on topic of compilers making undefined behavior based
optimizations).  Still not that nice from a logical point of view!

>  }
>  
>  module_init(einj_init);

Re: [PATCH 2/3] driver core: faux: Quiet probe failures

[Jonathan Cameron]

On Fri, 6 Jun 2025 20:32:27 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> The acpi-einj conversion to faux_device_create() leads to a noisy error
> message when the error injection facility is disabled. Quiet the error as
> CXL error injection via ACPI expects the module to stay loaded even if the
> error injection facility is disabled.
> 
> This situation arose because CXL knows proper kernel named objects to
> trigger errors against, but acpi-einj knows how to perform the error
> injection. The injection mechanism is shared with non-CXL use cases. The
> result is CXL now has a module dependency on einj-core.ko, and init/probe
> failures are handled at runtime.
> 
> Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>

I guess this is fair enough. 

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/base/faux.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/base/faux.c b/drivers/base/faux.c
> index 934da77ca48b..f5fbda0a9a44 100644
> --- a/drivers/base/faux.c
> +++ b/drivers/base/faux.c
> @@ -170,7 +170,7 @@ struct faux_device *faux_device_create_with_groups(const char *name,
>  	 * successful is almost impossible to determine by the caller.
>  	 */
>  	if (!dev->driver) {
> -		dev_err(dev, "probe did not succeed, tearing down the device\n");
> +		dev_dbg(dev, "probe did not succeed, tearing down the device\n");
>  		faux_device_destroy(faux_dev);
>  		faux_dev = NULL;
>  	}

Re: [PATCH 1/3] driver core: faux: Suppress bind attributes

[Jonathan Cameron]

On Fri, 6 Jun 2025 20:32:26 -0700
Dan Williams <dan.j.williams@intel.com> wrote:

> faux_device_create() is almost a suitable candidate to replace
> platform_driver_probe() if not for the fact that faux_device_create()
> supports dynamic attach/detach of the driver.
> 
> Drop the bind attributes with the expectation that simple faux devices can
> always assume that the device is permanently bound at create, and only
> unbound at 'destroy'.
> 
> The acpi-einj driver depends on static bind.
> 
> Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Seems like a fair assumption that these should never be used so
we might as well hide the.

Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/base/faux.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/base/faux.c b/drivers/base/faux.c
> index 9054d346bd7f..934da77ca48b 100644
> --- a/drivers/base/faux.c
> +++ b/drivers/base/faux.c
> @@ -86,6 +86,7 @@ static struct device_driver faux_driver = {
>  	.name		= "faux_driver",
>  	.bus		= &faux_bus_type,
>  	.probe_type	= PROBE_FORCE_SYNCHRONOUS,
> +	.suppress_bind_attrs = true,
>  };
>  
>  static void faux_device_release(struct device *dev)

Re: [PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Greg KH]

On Mon, Jun 09, 2025 at 11:17:58AM +0100, Jonathan Cameron wrote:
> On Fri, 6 Jun 2025 20:32:28 -0700
> Dan Williams <dan.j.williams@intel.com> wrote:
> 
> > CXL has a symbol dependency on einj_core.ko, so if einj_init() fails then
> > cxl_core.ko fails to load. Prior to the faux_device_create() conversion,
> > einj_probe() failures were tracked by the einj_initialized flag without
> > failing einj_init().
> > 
> > Revert to that behavior and always succeed einj_init() given there is no
> > way, and no pressing need, to discern faux device-create vs device-probe
> > failures.
> > 
> > This situation arose because CXL knows proper kernel named objects to
> > trigger errors against, but acpi-einj knows how to perform the error
> > injection. The injection mechanism is shared with non-CXL use cases. The
> > result is CXL now has a module dependency on einj-core.ko, and init/probe
> > failures are handled at runtime.
> > 
> > Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > Cc: Sudeep Holla <sudeep.holla@arm.com>
> > Cc: Ben Cheatham <Benjamin.Cheatham@amd.com>
> > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > ---
> >  drivers/acpi/apei/einj-core.c | 9 +++------
> >  1 file changed, 3 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
> > index fea11a35eea3..9b041415a9d0 100644
> > --- a/drivers/acpi/apei/einj-core.c
> > +++ b/drivers/acpi/apei/einj-core.c
> > @@ -883,19 +883,16 @@ static int __init einj_init(void)
> >  	}
> >  
> >  	einj_dev = faux_device_create("acpi-einj", NULL, &einj_device_ops);
> > -	if (!einj_dev)
> > -		return -ENODEV;
> >  
> > -	einj_initialized = true;
> > +	if (einj_dev)
> > +		einj_initialized = true;
> >  
> >  	return 0;
> >  }
> >  
> >  static void __exit einj_exit(void)
> >  {
> > -	if (einj_initialized)
> > -		faux_device_destroy(einj_dev);
> > -
> > +	faux_device_destroy(einj_dev);
> 
> Hi Dan,
> 
> Thi bit is sort of fine though not really related, because
> faux_device_destroy() checks
> 
> void faux_device_destroy(struct faux_device *faux_dev)
> {
> 	struct device *dev = &faux_dev->dev;
> 
> 	if (!faux_dev)
> 		return;
> 
> Though that check is after a dereference of faux_dev
> which doesn't look right to me.  Might be fine because
> of how the kernel is built (I can't remember where we ended
> up on topic of compilers making undefined behavior based
> optimizations).  Still not that nice from a logical point of view!

I think this is fine as we just put "0 + offset of dev" into dev, and
didn't do anything with that (i.e. no actual read of that memory
location happened).  The compiler shouldn't be doing anything that could
happen after the return before we check for a valid pointer here, right?

thanks,

greg k-h

Re: [PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Cheatham, Benjamin]

On 6/6/2025 10:32 PM, Dan Williams wrote:
> CXL has a symbol dependency on einj_core.ko, so if einj_init() fails then
> cxl_core.ko fails to load. Prior to the faux_device_create() conversion,
> einj_probe() failures were tracked by the einj_initialized flag without
> failing einj_init().
> 
> Revert to that behavior and always succeed einj_init() given there is no
> way, and no pressing need, to discern faux device-create vs device-probe
> failures.
> 
> This situation arose because CXL knows proper kernel named objects to
> trigger errors against, but acpi-einj knows how to perform the error
> injection. The injection mechanism is shared with non-CXL use cases. The
> result is CXL now has a module dependency on einj-core.ko, and init/probe
> failures are handled at runtime.
> 
> Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> Cc: Sudeep Holla <sudeep.holla@arm.com>
> Cc: Ben Cheatham <Benjamin.Cheatham@amd.com>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---

Thanks for sending this out!

Reviewed-by: Ben Cheatham <benjamin.cheatham@amd.com>

Re: [PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Sudeep Holla]

On Fri, Jun 06, 2025 at 08:32:25PM -0700, Dan Williams wrote:
> git bisect flags:
> 
> 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> 
> ...as the reason basic CXL unit tests are failing on latest mainline. In
> addition to the fix to einj-core.c, this also needs some updates to
> faux_device to make it behave more like platform_driver_probe(). Details
> in the individual patches.
> 

Thanks for not only reporting the issue with the commit above but also
solving it and posting patches.

They all look good to me.

Reviewed-by: Sudeep Holla <sudeep.holla@arm.com>

-- 
Regards,
Sudeep

Re: [PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Dave Jiang]

On 6/6/25 8:32 PM, Dan Williams wrote:
> git bisect flags:
> 
> 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> 
> ...as the reason basic CXL unit tests are failing on latest mainline. In
> addition to the fix to einj-core.c, this also needs some updates to
> faux_device to make it behave more like platform_driver_probe(). Details
> in the individual patches.
> 
> Dan Williams (3):
>   driver core: faux: Suppress bind attributes
>   driver core: faux: Quiet probe failures
>   ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create()
>     failure

LGTM
Reviewed-by: Dave Jiang <dave.jiang@intel.com>

> 
>  drivers/acpi/apei/einj-core.c | 9 +++------
>  drivers/base/faux.c           | 3 ++-
>  2 files changed, 5 insertions(+), 7 deletions(-)
> 
> 
> base-commit: a9dfb7db96f7bc1f30feae673aab7fdbfbc94e9c

Re: [PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Jonathan Cameron]

On Mon, 9 Jun 2025 12:42:53 +0200
Greg KH <gregkh@linuxfoundation.org> wrote:

> On Mon, Jun 09, 2025 at 11:17:58AM +0100, Jonathan Cameron wrote:
> > On Fri, 6 Jun 2025 20:32:28 -0700
> > Dan Williams <dan.j.williams@intel.com> wrote:
> >   
> > > CXL has a symbol dependency on einj_core.ko, so if einj_init() fails then
> > > cxl_core.ko fails to load. Prior to the faux_device_create() conversion,
> > > einj_probe() failures were tracked by the einj_initialized flag without
> > > failing einj_init().
> > > 
> > > Revert to that behavior and always succeed einj_init() given there is no
> > > way, and no pressing need, to discern faux device-create vs device-probe
> > > failures.
> > > 
> > > This situation arose because CXL knows proper kernel named objects to
> > > trigger errors against, but acpi-einj knows how to perform the error
> > > injection. The injection mechanism is shared with non-CXL use cases. The
> > > result is CXL now has a module dependency on einj-core.ko, and init/probe
> > > failures are handled at runtime.
> > > 
> > > Fixes: 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> > > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> > > Cc: Sudeep Holla <sudeep.holla@arm.com>
> > > Cc: Ben Cheatham <Benjamin.Cheatham@amd.com>
> > > Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> > > ---
> > >  drivers/acpi/apei/einj-core.c | 9 +++------
> > >  1 file changed, 3 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/drivers/acpi/apei/einj-core.c b/drivers/acpi/apei/einj-core.c
> > > index fea11a35eea3..9b041415a9d0 100644
> > > --- a/drivers/acpi/apei/einj-core.c
> > > +++ b/drivers/acpi/apei/einj-core.c
> > > @@ -883,19 +883,16 @@ static int __init einj_init(void)
> > >  	}
> > >  
> > >  	einj_dev = faux_device_create("acpi-einj", NULL, &einj_device_ops);
> > > -	if (!einj_dev)
> > > -		return -ENODEV;
> > >  
> > > -	einj_initialized = true;
> > > +	if (einj_dev)
> > > +		einj_initialized = true;
> > >  
> > >  	return 0;
> > >  }
> > >  
> > >  static void __exit einj_exit(void)
> > >  {
> > > -	if (einj_initialized)
> > > -		faux_device_destroy(einj_dev);
> > > -
> > > +	faux_device_destroy(einj_dev);  
> > 
> > Hi Dan,
> > 
> > Thi bit is sort of fine though not really related, because
> > faux_device_destroy() checks
> > 
> > void faux_device_destroy(struct faux_device *faux_dev)
> > {
> > 	struct device *dev = &faux_dev->dev;
> > 
> > 	if (!faux_dev)
> > 		return;
> > 
> > Though that check is after a dereference of faux_dev
> > which doesn't look right to me.  Might be fine because
> > of how the kernel is built (I can't remember where we ended
> > up on topic of compilers making undefined behavior based
> > optimizations).  Still not that nice from a logical point of view!  
> 
> I think this is fine as we just put "0 + offset of dev" into dev, and
> didn't do anything with that (i.e. no actual read of that memory
> location happened).  The compiler shouldn't be doing anything that could
> happen after the return before we check for a valid pointer here, right?

Hmm. I did some digging. Seems that was debated 10 years ago without
a huge amount of clarity on the answer beyond all sane people telling
compiler folk not to use this in optimizations :)

Comes down to whether any dereference of NULL is UB whether or not
the compiler can just do a simple offset calculation.

Anyhow, whilst fine, it's still a little ugly to my eyes :(

Jonathan



> 
> thanks,
> 
> greg k-h
> 

Re: [PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Rafael J. Wysocki]

On Mon, Jun 9, 2025 at 5:04 PM Dave Jiang <dave.jiang@intel.com> wrote:
>
>
>
> On 6/6/25 8:32 PM, Dan Williams wrote:
> > git bisect flags:
> >
> > 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> >
> > ...as the reason basic CXL unit tests are failing on latest mainline. In
> > addition to the fix to einj-core.c, this also needs some updates to
> > faux_device to make it behave more like platform_driver_probe(). Details
> > in the individual patches.
> >
> > Dan Williams (3):
> >   driver core: faux: Suppress bind attributes
> >   driver core: faux: Quiet probe failures
> >   ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create()
> >     failure
>
> LGTM
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
>
> >
> >  drivers/acpi/apei/einj-core.c | 9 +++------
> >  drivers/base/faux.c           | 3 ++-
> >  2 files changed, 5 insertions(+), 7 deletions(-)

Greg, I think it's better if I route this through the ACPI tree as the
issue being fixed was introduced through it.

Any concerns regarding this?

Re: [PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Greg KH]

On Mon, Jun 09, 2025 at 08:58:26PM +0200, Rafael J. Wysocki wrote:
> On Mon, Jun 9, 2025 at 5:04 PM Dave Jiang <dave.jiang@intel.com> wrote:
> >
> >
> >
> > On 6/6/25 8:32 PM, Dan Williams wrote:
> > > git bisect flags:
> > >
> > > 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> > >
> > > ...as the reason basic CXL unit tests are failing on latest mainline. In
> > > addition to the fix to einj-core.c, this also needs some updates to
> > > faux_device to make it behave more like platform_driver_probe(). Details
> > > in the individual patches.
> > >
> > > Dan Williams (3):
> > >   driver core: faux: Suppress bind attributes
> > >   driver core: faux: Quiet probe failures
> > >   ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create()
> > >     failure
> >
> > LGTM
> > Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> >
> > >
> > >  drivers/acpi/apei/einj-core.c | 9 +++------
> > >  drivers/base/faux.c           | 3 ++-
> > >  2 files changed, 5 insertions(+), 7 deletions(-)
> 
> Greg, I think it's better if I route this through the ACPI tree as the
> issue being fixed was introduced through it.
> 
> Any concerns regarding this?

None from me!

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Re: [PATCH 3/3] ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create() failure

[Dan Williams]

Jonathan Cameron wrote:
[..]
> Hmm. I did some digging. Seems that was debated 10 years ago without
> a huge amount of clarity on the answer beyond all sane people telling
> compiler folk not to use this in optimizations :)
> 
> Comes down to whether any dereference of NULL is UB whether or not
> the compiler can just do a simple offset calculation.
> 
> Anyhow, whilst fine, it's still a little ugly to my eyes :(

I recall we had this conversation with Dan Carpenter on a smatch patch
and resolved that while it looks "interesting" it does no harm.

For this patch I am not motivated to spin it because even if the the
compiler took advantage of the NULL check to drop UB work, that would
only mean dropping the assignment.

Otherwise, this conversion lines up with the intent of both
einj_initialized and faux_device_destroy() whereby faux_device_destroy()
is already prepared for the case where faux_device_create() fails.

Re: [PATCH 0/3] CXL: ACPI: faux: Fix cxl_core.ko module load regression

[Rafael J. Wysocki]

On Tue, Jun 10, 2025 at 12:12 PM Greg KH <gregkh@linuxfoundation.org> wrote:
>
> On Mon, Jun 09, 2025 at 08:58:26PM +0200, Rafael J. Wysocki wrote:
> > On Mon, Jun 9, 2025 at 5:04 PM Dave Jiang <dave.jiang@intel.com> wrote:
> > >
> > >
> > >
> > > On 6/6/25 8:32 PM, Dan Williams wrote:
> > > > git bisect flags:
> > > >
> > > > 6cb9441bfe8d ("ACPI: APEI: EINJ: Transition to the faux device interface")
> > > >
> > > > ...as the reason basic CXL unit tests are failing on latest mainline. In
> > > > addition to the fix to einj-core.c, this also needs some updates to
> > > > faux_device to make it behave more like platform_driver_probe(). Details
> > > > in the individual patches.
> > > >
> > > > Dan Williams (3):
> > > >   driver core: faux: Suppress bind attributes
> > > >   driver core: faux: Quiet probe failures
> > > >   ACPI: APEI: EINJ: Do not fail einj_init() on faux_device_create()
> > > >     failure
> > >
> > > LGTM
> > > Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> > >
> > > >
> > > >  drivers/acpi/apei/einj-core.c | 9 +++------
> > > >  drivers/base/faux.c           | 3 ++-
> > > >  2 files changed, 5 insertions(+), 7 deletions(-)
> >
> > Greg, I think it's better if I route this through the ACPI tree as the
> > issue being fixed was introduced through it.
> >
> > Any concerns regarding this?
>
> None from me!
>
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

So applied as 6.16-rc material.

Thank you!