[PATCH 0/2] hwmon: (coretemp) replace hardcoded core count and fix style issues

[PATCH 0/2] hwmon: (coretemp) replace hardcoded core count and fix style issues

[bakshansky.lists]

From: Roman Bakshansky <bakshansky.lists@gmail.com>

This series addresses a long-standing TODO in the coretemp driver by
replacing the hardcoded NUM_REAL_CORES with a dynamic per-package core
count. The second patch cleans up a few coding style warnings.

Roman Bakshansky (2):
  hwmon: (coretemp) replace hardcoded core count with dynamic value
  hwmon: (coretemp) fix coding style issues

 drivers/hwmon/coretemp.c | 21 +++++++--------------
 1 file changed, 7 insertions(+), 14 deletions(-)

--
2.53.0

[PATCH 1/2] hwmon: (coretemp) replace hardcoded core count with dynamic value

[bakshansky.lists]

From: Roman Bakshansky <bakshansky.lists@gmail.com>

The hardcoded maximum of 512 cores per package was first defined by commit
34cf8c657cf0 ("hwmon: (coretemp) Enlarge per package core count limit")
and later kept as a fallback with a TODO in commit 1a793caf6f69 ("hwmon:
(coretemp) Use dynamic allocated memory for core temp_data") because the
actual per-package core count was not reliably available at the time.

Now that topology_num_cores_per_package() is stable and suitable for use,
it's time to complete the TODO and allocate only the needed amount of
memory for core_data.

Signed-off-by: Roman Bakshansky <bakshansky.lists@gmail.com>
---
 drivers/hwmon/coretemp.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 6a0d94711ead..c722b1d8e480 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -39,7 +39,6 @@ static int force_tjmax;
 module_param_named(tjmax, force_tjmax, int, 0444);
 MODULE_PARM_DESC(tjmax, "TjMax value in degrees Celsius");
 
-#define NUM_REAL_CORES		512	/* Number of Real cores per cpu */
 #define CORETEMP_NAME_LENGTH	28	/* String Length of attrs */
 
 enum coretemp_attr_index {
@@ -485,13 +484,7 @@ init_temp_data(struct platform_data *pdata, unsigned int cpu, int pkg_flag)
 	struct temp_data *tdata;
 
 	if (!pdata->core_data) {
-		/*
-		 * TODO:
-		 * The information of actual possible cores in a package is broken for now.
-		 * Will replace hardcoded NUM_REAL_CORES with actual per package core count
-		 * when this information becomes available.
-		 */
-		pdata->nr_cores = NUM_REAL_CORES;
+		pdata->nr_cores = topology_num_cores_per_package();
 		pdata->core_data = kzalloc_objs(struct temp_data *,
 						pdata->nr_cores);
 		if (!pdata->core_data)
-- 
2.53.0

[PATCH 2/2] hwmon: (coretemp) fix coding style issues

[bakshansky.lists]

From: Roman Bakshansky <bakshansky.lists@gmail.com>

Address several coding style warnings reported by checkpatch.pl:
- Replace <asm/processor.h> with <linux/processor.h>
- Add missing blank lines after declarations
- Combine split quoted strings
- Reorder __initconst placement

No functional change.

Signed-off-by: Roman Bakshansky <bakshansky.lists@gmail.com>
---
 drivers/hwmon/coretemp.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index c722b1d8e480..a79c2d65a2be 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -25,7 +25,7 @@
 #include <linux/moduleparam.h>
 #include <linux/pci.h>
 #include <asm/msr.h>
-#include <asm/processor.h>
+#include <linux/processor.h>
 #include <asm/cpu_device_id.h>
 #include <linux/sched/isolation.h>
 
@@ -200,6 +200,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
 
 	for (i = 0; i < ARRAY_SIZE(tjmax_model_table); i++) {
 		const struct tjmax_model *tm = &tjmax_model_table[i];
+
 		if (c->x86_vfm == tm->vfm &&
 		    (tm->stepping_mask == ANY ||
 		     tm->stepping_mask == c->x86_stepping))
@@ -222,8 +223,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
 		err = rdmsr_safe_on_cpu(id, 0x17, &eax, &edx);
 		if (err) {
 			dev_warn(dev,
-				 "Unable to access MSR 0x17, assuming desktop"
-				 " CPU\n");
+				 "Unable to access MSR 0x17, assuming desktop CPU\n");
 			usemsr_ee = 0;
 		} else if (c->x86_vfm < INTEL_CORE2_PENRYN &&
 			   !(eax & 0x10000000)) {
@@ -257,8 +257,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
 		err = rdmsr_safe_on_cpu(id, 0xee, &eax, &edx);
 		if (err) {
 			dev_warn(dev,
-				 "Unable to access MSR 0xEE, for Tjmax, left"
-				 " at default\n");
+				 "Unable to access MSR 0xEE, for Tjmax, left at default\n");
 		} else if (eax & 0x40000000) {
 			tjmax = tjmax_ee;
 		}
@@ -424,6 +423,7 @@ static ssize_t show_temp(struct device *dev,
 static int create_core_attrs(struct temp_data *tdata, struct device *dev)
 {
 	int i;
+
 	static ssize_t (*const rd_ptr[TOTAL_ATTRS]) (struct device *dev,
 			struct device_attribute *devattr, char *buf) = {
 			show_label, show_crit_alarm, show_temp, show_tjmax,
@@ -774,7 +774,7 @@ static int coretemp_cpu_offline(unsigned int cpu)
 	}
 	return 0;
 }
-static const struct x86_cpu_id __initconst coretemp_ids[] = {
+static const struct x86_cpu_id coretemp_ids[] __initconst = {
 	X86_MATCH_VENDOR_FEATURE(INTEL, X86_FEATURE_DTHERM, NULL),
 	{}
 };
-- 
2.53.0

Re: [PATCH 1/2] hwmon: (coretemp) replace hardcoded core count with dynamic value

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
- [High] If `topology_num_cores_per_package()` evaluates to 0, an integer underflow occurs leading to an out-of-bounds write and kernel panic.
- [High] Using the global `topology_num_cores_per_package()` limits the per-package array size, preventing sensor initialization on heterogeneous packages or during CPU hot-add.
--

commit d686b3577dd2107e7452adf6a949cc0720d2213a
Author: Roman Bakshansky <bakshansky.lists@gmail.com>

hwmon: (coretemp) replace hardcoded core count with dynamic value

This commit replaces the hardcoded limit of 512 cores per package with
a dynamic value. It uses topology_num_cores_per_package() to allocate
only the needed amount of memory for core_data.

> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 6a0d94711eadb..c722b1d8e4804 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c

[ ... ]

> @@ -485,13 +484,7 @@ init_temp_data(struct platform_data *pdata, unsigned int cpu, int pkg_flag)
>  	struct temp_data *tdata;
>  
>  	if (!pdata->core_data) {
> -		/*
> -		 * TODO:
> -		 * The information of actual possible cores in a package is broken for now.
> -		 * Will replace hardcoded NUM_REAL_CORES with actual per package core count
> -		 * when this information becomes available.
> -		 */
> -		pdata->nr_cores = NUM_REAL_CORES;
> +		pdata->nr_cores = topology_num_cores_per_package();

Since topology_num_cores_per_package() returns a global value that is set
once during boot, could this prevent sensor initialization on heterogeneous
packages or during CPU hot-add?

In asymmetric multi-package architectures where a secondary package has more
cores than the primary, or when virtual CPUs are hot-added, pdata->nr_cores
would be capped at the primary package's boot core count. When initializing
extra cores, ida_alloc_max() would enforce this bound and return -ENOSPC,
silently dropping temperature sensors for valid cores.

Additionally, could topology_num_cores_per_package() return 0 if the CPU
topology is broken or misconfigured by a hypervisor?

> +		pdata->core_data = kzalloc_objs(struct temp_data *,
> +						pdata->nr_cores);
>  		if (!pdata->core_data)
>  			return NULL;

If pdata->nr_cores is 0, kzalloc_objs() will allocate 0 bytes and return the
kernel's ZERO_SIZE_PTR instead of NULL, bypassing this error check.

Later in this function, the index is allocated:

	} else {
		tdata->index = ida_alloc_max(&pdata->ida, pdata->nr_cores - 1, GFP_KERNEL);

If pdata->nr_cores is 0, the maximum bound (0 - 1) evaluates to -1, which
implicitly casts to UINT_MAX. ida_alloc_max() would accept this large bound
and return a valid index.

		if (tdata->index < 0) {
			kfree(tdata);
			return NULL;
		}
		pdata->core_data[tdata->index] = tdata;

Could this result in an attempt to write to the ZERO_SIZE_PTR address,
causing an unhandled page fault and kernel panic?

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260516114253.5466-1-bakshansky.lists@gmail.com?part=1

Re: [PATCH 2/2] hwmon: (coretemp) fix coding style issues

[sashiko-bot]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Low] A blank line was incorrectly added inside a contiguous block of declarations in `create_core_attrs()`, splitting the variable declarations.
--

commit fd6a696ecbdee696c6e67fb77fb06e3c1baa31cc
Author: Roman Bakshansky <bakshansky.lists@gmail.com>

hwmon: (coretemp) fix coding style issues

This commit addresses several coding style warnings reported by checkpatch.pl.
It updates header inclusions, adds missing blank lines, combines split strings,
and reorders the __initconst attribute.

> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index c722b1d8e4804..a79c2d65a2bee 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
[ ... ]
> @@ -424,6 +423,7 @@ static ssize_t show_temp(struct device *dev,
>  static int create_core_attrs(struct temp_data *tdata, struct device *dev)
>  {
>  	int i;
> +

This isn't a bug, but does this newly added blank line split a contiguous
block of variable declarations?

The static array rd_ptr is also a variable declaration, so this separates it
from the int i declaration. It looks like checkpatch.pl might have misparsed
the complex function pointer array declaration as a statement.

>  	static ssize_t (*const rd_ptr[TOTAL_ATTRS]) (struct device *dev,
>  			struct device_attribute *devattr, char *buf) = {
>  			show_label, show_crit_alarm, show_temp, show_tjmax,
>  			show_ttarget };

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20260516114253.5466-1-bakshansky.lists@gmail.com?part=2

Re: [PATCH 1/2] hwmon: (coretemp) replace hardcoded core count with dynamic value

[Guenter Roeck]

On 5/16/26 05:16, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [High] If `topology_num_cores_per_package()` evaluates to 0, an integer underflow occurs leading to an out-of-bounds write and kernel panic.
> - [High] Using the global `topology_num_cores_per_package()` limits the per-package array size, preventing sensor initialization on heterogeneous packages or during CPU hot-add.
> --
> 
> commit d686b3577dd2107e7452adf6a949cc0720d2213a
> Author: Roman Bakshansky <bakshansky.lists@gmail.com>
> 
> hwmon: (coretemp) replace hardcoded core count with dynamic value
> 
> This commit replaces the hardcoded limit of 512 cores per package with
> a dynamic value. It uses topology_num_cores_per_package() to allocate
> only the needed amount of memory for core_data.
> 
>> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
>> index 6a0d94711eadb..c722b1d8e4804 100644
>> --- a/drivers/hwmon/coretemp.c
>> +++ b/drivers/hwmon/coretemp.c
> 
> [ ... ]
> 
>> @@ -485,13 +484,7 @@ init_temp_data(struct platform_data *pdata, unsigned int cpu, int pkg_flag)
>>   	struct temp_data *tdata;
>>   
>>   	if (!pdata->core_data) {
>> -		/*
>> -		 * TODO:
>> -		 * The information of actual possible cores in a package is broken for now.
>> -		 * Will replace hardcoded NUM_REAL_CORES with actual per package core count
>> -		 * when this information becomes available.
>> -		 */
>> -		pdata->nr_cores = NUM_REAL_CORES;
>> +		pdata->nr_cores = topology_num_cores_per_package();
> 
> Since topology_num_cores_per_package() returns a global value that is set
> once during boot, could this prevent sensor initialization on heterogeneous
> packages or during CPU hot-add?
> 
> In asymmetric multi-package architectures where a secondary package has more
> cores than the primary, or when virtual CPUs are hot-added, pdata->nr_cores
> would be capped at the primary package's boot core count. When initializing
> extra cores, ida_alloc_max() would enforce this bound and return -ENOSPC,
> silently dropping temperature sensors for valid cores.
> 
> Additionally, could topology_num_cores_per_package() return 0 if the CPU
> topology is broken or misconfigured by a hypervisor?
> 

Per the submitter's statement, topology_num_cores_per_package() is stable.
Other use in the kernel suggests that it can not return 0 (that would
trigger a divide-by-zero crash), and other users seem to trust it.
Given that, I assume the concerns raised are not valid, and I am going
to apply this patch.

Thanks,
Guenter

>> +		pdata->core_data = kzalloc_objs(struct temp_data *,
>> +						pdata->nr_cores);
>>   		if (!pdata->core_data)
>>   			return NULL;
> 
> If pdata->nr_cores is 0, kzalloc_objs() will allocate 0 bytes and return the
> kernel's ZERO_SIZE_PTR instead of NULL, bypassing this error check.
> 
> Later in this function, the index is allocated:
> 
> 	} else {
> 		tdata->index = ida_alloc_max(&pdata->ida, pdata->nr_cores - 1, GFP_KERNEL);
> 
> If pdata->nr_cores is 0, the maximum bound (0 - 1) evaluates to -1, which
> implicitly casts to UINT_MAX. ida_alloc_max() would accept this large bound
> and return a valid index.
> 
> 		if (tdata->index < 0) {
> 			kfree(tdata);
> 			return NULL;
> 		}
> 		pdata->core_data[tdata->index] = tdata;
> 
> Could this result in an attempt to write to the ZERO_SIZE_PTR address,
> causing an unhandled page fault and kernel panic?
> 

Re: [PATCH 1/2] hwmon: (coretemp) replace hardcoded core count with dynamic value

[Guenter Roeck]

On Sat, May 16, 2026 at 02:42:52PM +0300, bakshansky.lists@gmail.com wrote:
> From: Roman Bakshansky <bakshansky.lists@gmail.com>
> 
> The hardcoded maximum of 512 cores per package was first defined by commit
> 34cf8c657cf0 ("hwmon: (coretemp) Enlarge per package core count limit")
> and later kept as a fallback with a TODO in commit 1a793caf6f69 ("hwmon:
> (coretemp) Use dynamic allocated memory for core temp_data") because the
> actual per-package core count was not reliably available at the time.
> 
> Now that topology_num_cores_per_package() is stable and suitable for use,
> it's time to complete the TODO and allocate only the needed amount of
> memory for core_data.
> 
> Signed-off-by: Roman Bakshansky <bakshansky.lists@gmail.com>

Applied.

Thanks,
Guenter

Re: [PATCH 2/2] hwmon: (coretemp) fix coding style issues

[Guenter Roeck]

On Sat, May 16, 2026 at 02:42:53PM +0300, bakshansky.lists@gmail.com wrote:
> From: Roman Bakshansky <bakshansky.lists@gmail.com>
> 
> Address several coding style warnings reported by checkpatch.pl:
> - Replace <asm/processor.h> with <linux/processor.h>
> - Add missing blank lines after declarations
> - Combine split quoted strings
> - Reorder __initconst placement
> 
> No functional change.
> 
> Signed-off-by: Roman Bakshansky <bakshansky.lists@gmail.com>
> ---
>  drivers/hwmon/coretemp.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index c722b1d8e480..a79c2d65a2be 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -25,7 +25,7 @@
>  #include <linux/moduleparam.h>
>  #include <linux/pci.h>
>  #include <asm/msr.h>
> -#include <asm/processor.h>
> +#include <linux/processor.h>
>  #include <asm/cpu_device_id.h>
>  #include <linux/sched/isolation.h>
>  
> @@ -200,6 +200,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
>  
>  	for (i = 0; i < ARRAY_SIZE(tjmax_model_table); i++) {
>  		const struct tjmax_model *tm = &tjmax_model_table[i];
> +
>  		if (c->x86_vfm == tm->vfm &&
>  		    (tm->stepping_mask == ANY ||
>  		     tm->stepping_mask == c->x86_stepping))
> @@ -222,8 +223,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
>  		err = rdmsr_safe_on_cpu(id, 0x17, &eax, &edx);
>  		if (err) {
>  			dev_warn(dev,
> -				 "Unable to access MSR 0x17, assuming desktop"
> -				 " CPU\n");
> +				 "Unable to access MSR 0x17, assuming desktop CPU\n");
>  			usemsr_ee = 0;
>  		} else if (c->x86_vfm < INTEL_CORE2_PENRYN &&
>  			   !(eax & 0x10000000)) {
> @@ -257,8 +257,7 @@ static int adjust_tjmax(struct cpuinfo_x86 *c, u32 id, struct device *dev)
>  		err = rdmsr_safe_on_cpu(id, 0xee, &eax, &edx);
>  		if (err) {
>  			dev_warn(dev,
> -				 "Unable to access MSR 0xEE, for Tjmax, left"
> -				 " at default\n");
> +				 "Unable to access MSR 0xEE, for Tjmax, left at default\n");
>  		} else if (eax & 0x40000000) {
>  			tjmax = tjmax_ee;
>  		}
> @@ -424,6 +423,7 @@ static ssize_t show_temp(struct device *dev,
>  static int create_core_attrs(struct temp_data *tdata, struct device *dev)
>  {
>  	int i;
> +

As pointed out by Sashiko, this is a false positive.

>  	static ssize_t (*const rd_ptr[TOTAL_ATTRS]) (struct device *dev,
>  			struct device_attribute *devattr, char *buf) = {
>  			show_label, show_crit_alarm, show_temp, show_tjmax,
> @@ -774,7 +774,7 @@ static int coretemp_cpu_offline(unsigned int cpu)
>  	}
>  	return 0;
>  }
> -static const struct x86_cpu_id __initconst coretemp_ids[] = {
> +static const struct x86_cpu_id coretemp_ids[] __initconst = {

checkpatch says:

CHECK: Please use a blank line after function/struct/union/enum declarations
#170: FILE: drivers/hwmon/coretemp.c:777:
 }
+static const struct x86_cpu_id coretemp_ids[] __initconst = {

Oh never mind, I'll fix that up and apply the patch.

Guenter

Re: [PATCH 2/2] hwmon: (coretemp) fix coding style issues

[bakshansky.lists]

> Oh never mind, I'll fix that up and apply the patch.
> 
> Guenter

Thank you for fixing that and for taking the patches, Guenter. This was my
first contribution to the kernel, and your review made it a great experience.
I appreciate it.

Roman