[PATCH v5] cxl/core: Create einj_types regardless of EINJ init order

[PATCH v5] cxl/core: Create einj_types regardless of EINJ init order

[Yongxin Yang]

The einj_types file under the CXL debugfs directory is never created when
cxl_core is built in.  cxl_core_init() runs at subsys_initcall level, while
einj_init() registers EINJ at device_initcall level, so the
einj_cxl_is_initialized() check in cxl_core_init() always sees EINJ as not
up yet and the debugfs_create_file() below it is never reached.  With
cxl_core as a module, module dependencies make sure it is loaded after EINJ
is up and the file is created.

Create the file unconditionally instead, gated only on the CXL error
injection support being compiled in, and have
einj_cxl_available_error_type_show() return -ENODEV until EINJ is up.  This
single check in cxl_core_init() covers every combination of built-in and
modular cxl_core, cxl_acpi and EINJ, with no extra hooks.

The check in the show callback is required, not cosmetic: einj_tab is
NULL until einj_init() runs, so einj_get_available_error_type() would
dereference a NULL pointer.

This restores the discovery of the supported error types only.  On a fully
built-in RCH/RCD hierarchy the inject files below the dport directory are
still not created: cxl_debugfs_create_dport_dir() has the same early return
and the only dport there comes from cxl_acpi_probe() at
subsys_initcall_sync level, before EINJ is up.

Fixes: 8039804cfa73 ("cxl/core: Add CXL EINJ debugfs files")
Cc: <stable@vger.kernel.org>
Suggested-by: Dave Jiang <dave.jiang@intel.com>
Suggested-by: Ben Cheatham <benjamin.cheatham@amd.com>
Link: https://lore.kernel.org/all/de14c4ef-e3d8-432f-9ce8-87c468d6d2ad@amd.com/
Link: https://lore.kernel.org/all/7a22cc6a-deba-40e6-8033-97d1234420ba@amd.com/
Signed-off-by: Yongxin Yang <yangyongxin@kylinos.cn>
---
Changes in v5:
- Rework per Dave's suggestion, agreed by Ben: create einj_types from
  cxl_core_init() without looking at the runtime EINJ state, and return
  -ENODEV from einj_cxl_available_error_type_show() while EINJ is not
  initialized, instead of creating the file from three separate hooks.
  This drops the mutex, the exported helper and the cached dentry.
- Drop the cxl_acpi_probe() hook: host bridge dports, RCH included, already
  go through __devm_cxl_add_dport() -> cxl_debugfs_create_dport_dir() in the
  same probe, so the hook added nothing.
- Gate the creation on CONFIG_ACPI_APEI_EINJ_CXL rather than on the runtime
  EINJ state.
- Dropped the Reviewed-by tag as the approach changed significantly.

 drivers/acpi/apei/einj-cxl.c | 4 ++++
 drivers/cxl/core/port.c      | 2 +-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/apei/einj-cxl.c b/drivers/acpi/apei/einj-cxl.c
index e70a416ec925..3090c7649ed2 100644
--- a/drivers/acpi/apei/einj-cxl.c
+++ b/drivers/acpi/apei/einj-cxl.c
@@ -30,6 +30,10 @@ int einj_cxl_available_error_type_show(struct seq_file *m, void *v)
 	int cxl_err, rc;
 	u32 available_error_type = 0;
 
+	/* einj_tab stays NULL until EINJ is initialized, don't read it. */
+	if (!einj_cxl_is_initialized())
+		return -ENODEV;
+
 	rc = einj_get_available_error_type(&available_error_type, ACPI_EINJ_GET_ERROR_TYPE);
 	if (rc)
 		return rc;
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 625e4aa427db..d4ed1cc7c480 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -2515,7 +2515,7 @@ static __init int cxl_core_init(void)
 
 	cxl_debugfs = debugfs_create_dir("cxl", NULL);
 
-	if (einj_cxl_is_initialized())
+	if (IS_ENABLED(CONFIG_ACPI_APEI_EINJ_CXL))
 		debugfs_create_file("einj_types", 0400, cxl_debugfs, NULL,
 				    &einj_cxl_available_error_type_fops);
 
-- 
2.25.1

Re: [PATCH v5] cxl/core: Create einj_types regardless of EINJ init order

[Cheatham, Benjamin]

On 11/1/2026 9:24 PM, Yongxin Yang wrote:
> [You don't often get email from yangyongxin@kylinos.cn. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> The einj_types file under the CXL debugfs directory is never created when
> cxl_core is built in.  cxl_core_init() runs at subsys_initcall level, while
> einj_init() registers EINJ at device_initcall level, so the
> einj_cxl_is_initialized() check in cxl_core_init() always sees EINJ as not
> up yet and the debugfs_create_file() below it is never reached.  With
> cxl_core as a module, module dependencies make sure it is loaded after EINJ
> is up and the file is created.
> 
> Create the file unconditionally instead, gated only on the CXL error
> injection support being compiled in, and have
> einj_cxl_available_error_type_show() return -ENODEV until EINJ is up.  This
> single check in cxl_core_init() covers every combination of built-in and
> modular cxl_core, cxl_acpi and EINJ, with no extra hooks.

The first sentence makes no sense, it says it is created unconditionally and
then lists a condition for it to be created XD. Second sentence in unnecessary
as well, you already mentioned the module case is fine above. I'd change to
something like: "Change the file creation condition from EINJ being initialized
to a compile time check for ACPI_APEI_EINJ_CXL and return -ENODEV until EINJ
is up."
> 
> The check in the show callback is required, not cosmetic: einj_tab is
> NULL until einj_init() runs, so einj_get_available_error_type() would
> dereference a NULL pointer.
> 

This is pretty self-explanatory in the code, I'd remove this part.

> This restores the discovery of the supported error types only.  On a fully
> built-in RCH/RCD hierarchy the inject files below the dport directory are
> still not created: cxl_debugfs_create_dport_dir() has the same early return
> and the only dport there comes from cxl_acpi_probe() at
> subsys_initcall_sync level, before EINJ is up.

I'm looking at this now and this doesn't need to be the case. We can do the same
thing in cxl_debugfs_create_dport_dir() and replace the "if (!einj_cxl_is_initialized())"
with "if (IS_ENABLED(CONFIG_ACPI_APEI_EINJ_CXL))", then modify cxl_einj_inject() to do
check einj_cxl_is_initialized() before doing anything.

Also, this function isn't broken for RCH ports specifically, it's all downstream ports...
> 
> Fixes: 8039804cfa73 ("cxl/core: Add CXL EINJ debugfs files")
> Cc: <stable@vger.kernel.org>

I don't think this is big enough to be backported to stable. This functionality isn't very
heavily used, and the config where it's broken isn't what most people use AFAIK.
> Suggested-by: Dave Jiang <dave.jiang@intel.com>
> Suggested-by: Ben Cheatham <benjamin.cheatham@amd.com>

Suggested-by tags are for when the original change was suggested by the party, not
when they have review suggestions.

> Link: https://lore.kernel.org/all/de14c4ef-e3d8-432f-9ce8-87c468d6d2ad@amd.com/
> Link: https://lore.kernel.org/all/7a22cc6a-deba-40e6-8033-97d1234420ba@amd.com/

These probably shouldn't be here, you can put links to the past revisions under the git marker ("---")
below though if you feel so inclined.
> Signed-off-by: Yongxin Yang <yangyongxin@kylinos.cn>
> ---
> Changes in v5:
> - Rework per Dave's suggestion, agreed by Ben: create einj_types from
>   cxl_core_init() without looking at the runtime EINJ state, and return
>   -ENODEV from einj_cxl_available_error_type_show() while EINJ is not
>   initialized, instead of creating the file from three separate hooks.
>   This drops the mutex, the exported helper and the cached dentry.
> - Drop the cxl_acpi_probe() hook: host bridge dports, RCH included, already
>   go through __devm_cxl_add_dport() -> cxl_debugfs_create_dport_dir() in the
>   same probe, so the hook added nothing.
> - Gate the creation on CONFIG_ACPI_APEI_EINJ_CXL rather than on the runtime
>   EINJ state.
> - Dropped the Reviewed-by tag as the approach changed significantly.
> 
>  drivers/acpi/apei/einj-cxl.c | 4 ++++
>  drivers/cxl/core/port.c      | 2 +-
>  2 files changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/acpi/apei/einj-cxl.c b/drivers/acpi/apei/einj-cxl.c
> index e70a416ec925..3090c7649ed2 100644
> --- a/drivers/acpi/apei/einj-cxl.c
> +++ b/drivers/acpi/apei/einj-cxl.c
> @@ -30,6 +30,10 @@ int einj_cxl_available_error_type_show(struct seq_file *m, void *v)
>         int cxl_err, rc;
>         u32 available_error_type = 0;
> 
> +       /* einj_tab stays NULL until EINJ is initialized, don't read it. */

Remove this comment, it's redundant in this situation.

Thanks,
Ben

> +       if (!einj_cxl_is_initialized())
> +               return -ENODEV;
> +
>         rc = einj_get_available_error_type(&available_error_type, ACPI_EINJ_GET_ERROR_TYPE);
>         if (rc)
>                 return rc;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index 625e4aa427db..d4ed1cc7c480 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -2515,7 +2515,7 @@ static __init int cxl_core_init(void)
> 
>         cxl_debugfs = debugfs_create_dir("cxl", NULL);
> 
> -       if (einj_cxl_is_initialized())
> +       if (IS_ENABLED(CONFIG_ACPI_APEI_EINJ_CXL))
>                 debugfs_create_file("einj_types", 0400, cxl_debugfs, NULL,
>                                     &einj_cxl_available_error_type_fops);
> 
> --
> 2.25.1
> 

[PATCH v6] cxl/core: Create EINJ debugfs files regardless of EINJ init order

[Yongxin Yang]

The einj_types file under the CXL debugfs directory is never created when
cxl_core is built in.  cxl_core_init() runs at subsys_initcall level, while
einj_init() registers EINJ at device_initcall level, so the
einj_cxl_is_initialized() check in cxl_core_init() always sees EINJ as not
up yet and the debugfs_create_file() below it is never reached.

Change the file creation condition from EINJ being initialized to a compile
time check for ACPI_APEI_EINJ_CXL and return -ENODEV until EINJ is up.

The same check also guards the inject files under every downstream port
directory, not just the RCH ones.  Gate that directory creation on
CONFIG_ACPI_APEI_EINJ_CXL as well, and check einj_cxl_is_initialized() in
cxl_einj_inject() to reject writes until EINJ is up.

Fixes: 8039804cfa73 ("cxl/core: Add CXL EINJ debugfs files")
Signed-off-by: Yongxin Yang <yangyongxin@kylinos.cn>
---
Link: https://lore.kernel.org/all/de14c4ef-e3d8-432f-9ce8-87c468d6d2ad@amd.com/
Link: https://lore.kernel.org/all/7a22cc6a-deba-40e6-8033-97d1234420ba@amd.com/

Changes in v6:
- Apply the same compile time check to cxl_debugfs_create_dport_dir() and
  move the runtime check into cxl_einj_inject(), so the inject files under
  the downstream ports are created as well.  This is not RCH specific, all
  downstream ports are affected.
- Reword the commit log as suggested and drop the parts that the code makes
  obvious.
- Drop Cc: stable and both Suggested-by tags, move the lore links below the
  git marker.

 drivers/acpi/apei/einj-cxl.c | 3 +++
 drivers/cxl/core/port.c      | 7 +++++--
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/acpi/apei/einj-cxl.c b/drivers/acpi/apei/einj-cxl.c
index e70a416ec925..22a7eb4dc75e 100644
--- a/drivers/acpi/apei/einj-cxl.c
+++ b/drivers/acpi/apei/einj-cxl.c
@@ -30,6 +30,9 @@ int einj_cxl_available_error_type_show(struct seq_file *m, void *v)
 	int cxl_err, rc;
 	u32 available_error_type = 0;
 
+	if (!einj_cxl_is_initialized())
+		return -ENODEV;
+
 	rc = einj_get_available_error_type(&available_error_type, ACPI_EINJ_GET_ERROR_TYPE);
 	if (rc)
 		return rc;
diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
index 625e4aa427db..a949228de936 100644
--- a/drivers/cxl/core/port.c
+++ b/drivers/cxl/core/port.c
@@ -806,6 +806,9 @@ static int cxl_einj_inject(void *data, u64 type)
 {
 	struct cxl_dport *dport = data;
 
+	if (!einj_cxl_is_initialized())
+		return -ENODEV;
+
 	if (dport->rch)
 		return einj_cxl_inject_rch_error(dport->rcrb.base, type);
 
@@ -819,7 +822,7 @@ static void cxl_debugfs_create_dport_dir(struct cxl_dport *dport)
 	struct cxl_port *parent = parent_port_of(dport->port);
 	struct dentry *dir;
 
-	if (!einj_cxl_is_initialized())
+	if (!IS_ENABLED(CONFIG_ACPI_APEI_EINJ_CXL))
 		return;
 
 	/*
@@ -2515,7 +2518,7 @@ static __init int cxl_core_init(void)
 
 	cxl_debugfs = debugfs_create_dir("cxl", NULL);
 
-	if (einj_cxl_is_initialized())
+	if (IS_ENABLED(CONFIG_ACPI_APEI_EINJ_CXL))
 		debugfs_create_file("einj_types", 0400, cxl_debugfs, NULL,
 				    &einj_cxl_available_error_type_fops);
 
-- 
2.25.1