[PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Marcelo Tosatti]

The coretemp driver uses rdmsr_on_cpu calls to read
MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
which contain information about current core temperature.

For certain low latency applications, the RDMSR interruption exceeds    
the applications requirements.

So disable reading of crit_alarm and temp files via /sys, in case
CPU isolation is enabled.

Temperature information from the housekeeping cores should be
sufficient to infer die temperature.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 9bee4d33fbdf..30a35f4130d5 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -27,6 +27,7 @@
 #include <asm/msr.h>
 #include <asm/processor.h>
 #include <asm/cpu_device_id.h>
+#include <linux/sched/isolation.h>
 
 #define DRVNAME	"coretemp"
 
@@ -121,6 +122,10 @@ static ssize_t show_crit_alarm(struct device *dev,
 	struct platform_data *pdata = dev_get_drvdata(dev);
 	struct temp_data *tdata = pdata->core_data[attr->index];
 
+
+	if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+		return -EINVAL;
+
 	mutex_lock(&tdata->update_lock);
 	rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
 	mutex_unlock(&tdata->update_lock);
@@ -158,6 +163,8 @@ static ssize_t show_temp(struct device *dev,
 
 	/* Check whether the time interval has elapsed */
 	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
+		if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+			return -EINVAL;
 		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
 		/*
 		 * Ignore the valid bit. In all observed cases the register

Re: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Guenter Roeck]

On 12/15/22 04:42, Marcelo Tosatti wrote:
> 
> The coretemp driver uses rdmsr_on_cpu calls to read
> MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
> which contain information about current core temperature.
> 
> For certain low latency applications, the RDMSR interruption exceeds
> the applications requirements.
> 
> So disable reading of crit_alarm and temp files via /sys, in case
> CPU isolation is enabled.
> 

That isn't really what the code is doing. It doesn't disable reading
the attributes, it returns an error when an attempt is made to read
them.

> Temperature information from the housekeeping cores should be
> sufficient to infer die temperature.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 9bee4d33fbdf..30a35f4130d5 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -27,6 +27,7 @@
>   #include <asm/msr.h>
>   #include <asm/processor.h>
>   #include <asm/cpu_device_id.h>
> +#include <linux/sched/isolation.h>
>   
>   #define DRVNAME	"coretemp"
>   
> @@ -121,6 +122,10 @@ static ssize_t show_crit_alarm(struct device *dev,
>   	struct platform_data *pdata = dev_get_drvdata(dev);
>   	struct temp_data *tdata = pdata->core_data[attr->index];
>   
> +
> +	if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
> +		return -EINVAL;


Littering the output of the "sensors" command with errors is most
definitely wrong and not acceptable. On top of that, the user didn't
do anything wrong, so -EINVAL ("Invalid Argument") is definitely
the wrong error. Maybe return -ENODATA, or if the condition is
static just don't instantiate the attribute for the affected CPUs
to start with. Also, this warrants a comment in the code and an
explanation in Documentation/hwmon/coretemp.rst.

Guenter

[PATCH v2] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Marcelo Tosatti]

The coretemp driver uses rdmsr_on_cpu calls to read
MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
which contain information about current core temperature.

For certain low latency applications, the RDMSR interruption exceeds
the applications requirements.

So disallow reading of crit_alarm and temp files via /sys, returning 
-EINVAL, in case CPU isolation is enabled.

Temperature information from the housekeeping cores should be
sufficient to infer die temperature.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
v2: improve changelog to mention that an error is returned,
    and sysfs file is not disabled (Guenter Roeck)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 9bee4d33fbdf..30a35f4130d5 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -27,6 +27,7 @@
 #include <asm/msr.h>
 #include <asm/processor.h>
 #include <asm/cpu_device_id.h>
+#include <linux/sched/isolation.h>
 
 #define DRVNAME	"coretemp"
 
@@ -121,6 +122,10 @@ static ssize_t show_crit_alarm(struct device *dev,
 	struct platform_data *pdata = dev_get_drvdata(dev);
 	struct temp_data *tdata = pdata->core_data[attr->index];
 
+
+	if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+		return -EINVAL;
+
 	mutex_lock(&tdata->update_lock);
 	rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
 	mutex_unlock(&tdata->update_lock);
@@ -158,6 +163,8 @@ static ssize_t show_temp(struct device *dev,
 
 	/* Check whether the time interval has elapsed */
 	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
+		if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
+			return -EINVAL;
 		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
 		/*
 		 * Ignore the valid bit. In all observed cases the register

Re: [PATCH v2] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Guenter Roeck]

On 12/16/22 06:07, Marcelo Tosatti wrote:
> 
> The coretemp driver uses rdmsr_on_cpu calls to read
> MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
> which contain information about current core temperature.
> 
> For certain low latency applications, the RDMSR interruption exceeds
> the applications requirements.
> 
> So disallow reading of crit_alarm and temp files via /sys, returning
> -EINVAL, in case CPU isolation is enabled.
> 
> Temperature information from the housekeeping cores should be
> sufficient to infer die temperature.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> 
> ---
> v2: improve changelog to mention that an error is returned,
>      and sysfs file is not disabled (Guenter Roeck)
> 

You did not address my feedback. I requested a code change.
Returning -EINVAL is unacceptable, and a solution not creating
the sysfs attributes to start with would be preferred.

Guenter

> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 9bee4d33fbdf..30a35f4130d5 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -27,6 +27,7 @@
>   #include <asm/msr.h>
>   #include <asm/processor.h>
>   #include <asm/cpu_device_id.h>
> +#include <linux/sched/isolation.h>
>   
>   #define DRVNAME	"coretemp"
>   
> @@ -121,6 +122,10 @@ static ssize_t show_crit_alarm(struct device *dev,
>   	struct platform_data *pdata = dev_get_drvdata(dev);
>   	struct temp_data *tdata = pdata->core_data[attr->index];
>   
> +
> +	if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
> +		return -EINVAL;
> +
>   	mutex_lock(&tdata->update_lock);
>   	rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
>   	mutex_unlock(&tdata->update_lock);
> @@ -158,6 +163,8 @@ static ssize_t show_temp(struct device *dev,
>   
>   	/* Check whether the time interval has elapsed */
>   	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
> +		if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
> +			return -EINVAL;
>   		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
>   		/*
>   		 * Ignore the valid bit. In all observed cases the register
> 
> 
> 
> 

[PATCH v3] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Marcelo Tosatti]

The coretemp driver uses rdmsr_on_cpu calls to read
MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
which contain information about current core temperature.

For certain low latency applications, the RDMSR interruption exceeds
the applications requirements.

So do not create core files in sysfs, for CPUs which have
isolation and nohz_full enabled.

Temperature information from the housekeeping cores should be
sufficient to infer die temperature.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
v3: do not create sysfs files for isolated CPUs (Guenter Roeck)
v2: improve changelog to mention that an error is returned,
     and sysfs file is not disabled (Guenter Roeck)

diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
index 9bee4d33fbdf..619dfde7a712 100644
--- a/drivers/hwmon/coretemp.c
+++ b/drivers/hwmon/coretemp.c
@@ -27,6 +27,7 @@
 #include <asm/msr.h>
 #include <asm/processor.h>
 #include <asm/cpu_device_id.h>
+#include <linux/sched/isolation.h>
 
 #define DRVNAME	"coretemp"
 
@@ -458,6 +459,9 @@ static int create_core_data(struct platform_device *pdev, unsigned int cpu,
 	u32 eax, edx;
 	int err, index, attr_no;
 
+	if (!housekeeping_cpu(cpu, HK_TYPE_MISC))
+		return 0;
+
 	/*
 	 * Find attr number for sysfs:
 	 * We map the attr number to core id of the CPU

Re: [PATCH v3] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Guenter Roeck]

On Fri, Dec 16, 2022 at 05:24:08PM -0300, Marcelo Tosatti wrote:
> The coretemp driver uses rdmsr_on_cpu calls to read
> MSR_IA32_PACKAGE_THERM_STATUS/MSR_IA32_THERM_STATUS registers,
> which contain information about current core temperature.
> 
> For certain low latency applications, the RDMSR interruption exceeds
> the applications requirements.
> 
> So do not create core files in sysfs, for CPUs which have
> isolation and nohz_full enabled.
> 
> Temperature information from the housekeeping cores should be
> sufficient to infer die temperature.
> 
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

Applied to hwmon-next.

Thanks,
Guenter

> ---
> v3: do not create sysfs files for isolated CPUs (Guenter Roeck)
> v2: improve changelog to mention that an error is returned,
>      and sysfs file is not disabled (Guenter Roeck)
> 
> diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c
> index 9bee4d33fbdf..619dfde7a712 100644
> --- a/drivers/hwmon/coretemp.c
> +++ b/drivers/hwmon/coretemp.c
> @@ -27,6 +27,7 @@
>  #include <asm/msr.h>
>  #include <asm/processor.h>
>  #include <asm/cpu_device_id.h>
> +#include <linux/sched/isolation.h>
>  
>  #define DRVNAME	"coretemp"
>  
> @@ -458,6 +459,9 @@ static int create_core_data(struct platform_device *pdev, unsigned int cpu,
>  	u32 eax, edx;
>  	int err, index, attr_no;
>  
> +	if (!housekeeping_cpu(cpu, HK_TYPE_MISC))
> +		return 0;
> +
>  	/*
>  	 * Find attr number for sysfs:
>  	 * We map the attr number to core id of the CPU

Re: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Dan Carpenter]

Hi Marcelo,

https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Marcelo-Tosatti/hwmon-coretemp-avoid-RDMSR-interruptions-to-isolated-CPUs/20221215-204904
patch link:    https://lore.kernel.org/r/Y5sWMEG0xCl9bgEi%40tpad
patch subject: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs
config: i386-randconfig-m021
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>

smatch warnings:
drivers/hwmon/coretemp.c:181 show_temp() warn: inconsistent returns '&tdata->update_lock'.

vim +181 drivers/hwmon/coretemp.c

199e0de7f5df31 Durgadoss R     2011-05-20  154  static ssize_t show_temp(struct device *dev,
199e0de7f5df31 Durgadoss R     2011-05-20  155  			struct device_attribute *devattr, char *buf)
199e0de7f5df31 Durgadoss R     2011-05-20  156  {
bebe467823c0d8 Rudolf Marek    2007-05-08  157  	u32 eax, edx;
199e0de7f5df31 Durgadoss R     2011-05-20  158  	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
199e0de7f5df31 Durgadoss R     2011-05-20  159  	struct platform_data *pdata = dev_get_drvdata(dev);
199e0de7f5df31 Durgadoss R     2011-05-20  160  	struct temp_data *tdata = pdata->core_data[attr->index];
199e0de7f5df31 Durgadoss R     2011-05-20  161  
199e0de7f5df31 Durgadoss R     2011-05-20  162  	mutex_lock(&tdata->update_lock);
bebe467823c0d8 Rudolf Marek    2007-05-08  163  
199e0de7f5df31 Durgadoss R     2011-05-20  164  	/* Check whether the time interval has elapsed */
199e0de7f5df31 Durgadoss R     2011-05-20  165  	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
e78264610cd902 Marcelo Tosatti 2022-12-15  166  		if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
e78264610cd902 Marcelo Tosatti 2022-12-15  167  			return -EINVAL;

mutex_unlock(&tdata->update_lock);

199e0de7f5df31 Durgadoss R     2011-05-20  168  		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
bf6ea084ebb54c Guenter Roeck   2013-11-20  169  		/*
bf6ea084ebb54c Guenter Roeck   2013-11-20  170  		 * Ignore the valid bit. In all observed cases the register
bf6ea084ebb54c Guenter Roeck   2013-11-20  171  		 * value is either low or zero if the valid bit is 0.
bf6ea084ebb54c Guenter Roeck   2013-11-20  172  		 * Return it instead of reporting an error which doesn't
bf6ea084ebb54c Guenter Roeck   2013-11-20  173  		 * really help at all.
bf6ea084ebb54c Guenter Roeck   2013-11-20  174  		 */
bf6ea084ebb54c Guenter Roeck   2013-11-20  175  		tdata->temp = tdata->tjmax - ((eax >> 16) & 0x7f) * 1000;
952a11ca32a604 Paul Fertser    2021-09-24  176  		tdata->valid = true;
199e0de7f5df31 Durgadoss R     2011-05-20  177  		tdata->last_updated = jiffies;
bebe467823c0d8 Rudolf Marek    2007-05-08  178  	}
bebe467823c0d8 Rudolf Marek    2007-05-08  179  
199e0de7f5df31 Durgadoss R     2011-05-20  180  	mutex_unlock(&tdata->update_lock);
bf6ea084ebb54c Guenter Roeck   2013-11-20 @181  	return sprintf(buf, "%d\n", tdata->temp);
bebe467823c0d8 Rudolf Marek    2007-05-08  182  }

-- 
0-DAY CI Kernel Test Service
https://01.org/lkp

Re: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

[Marcelo Tosatti]

On Fri, Dec 23, 2022 at 01:48:14PM +0300, Dan Carpenter wrote:
> Hi Marcelo,
> 
> https://git-scm.com/docs/git-format-patch#_base_tree_information]
> 
> url:    https://github.com/intel-lab-lkp/linux/commits/Marcelo-Tosatti/hwmon-coretemp-avoid-RDMSR-interruptions-to-isolated-CPUs/20221215-204904
> patch link:    https://lore.kernel.org/r/Y5sWMEG0xCl9bgEi%40tpad
> patch subject: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs
> config: i386-randconfig-m021
> compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
> 
> If you fix the issue, kindly add following tag where applicable
> | Reported-by: kernel test robot <lkp@intel.com>
> | Reported-by: Dan Carpenter <error27@gmail.com>
> 
> smatch warnings:
> drivers/hwmon/coretemp.c:181 show_temp() warn: inconsistent returns '&tdata->update_lock'.
> 
> vim +181 drivers/hwmon/coretemp.c
> 
> 199e0de7f5df31 Durgadoss R     2011-05-20  154  static ssize_t show_temp(struct device *dev,
> 199e0de7f5df31 Durgadoss R     2011-05-20  155  			struct device_attribute *devattr, char *buf)
> 199e0de7f5df31 Durgadoss R     2011-05-20  156  {
> bebe467823c0d8 Rudolf Marek    2007-05-08  157  	u32 eax, edx;
> 199e0de7f5df31 Durgadoss R     2011-05-20  158  	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
> 199e0de7f5df31 Durgadoss R     2011-05-20  159  	struct platform_data *pdata = dev_get_drvdata(dev);
> 199e0de7f5df31 Durgadoss R     2011-05-20  160  	struct temp_data *tdata = pdata->core_data[attr->index];
> 199e0de7f5df31 Durgadoss R     2011-05-20  161  
> 199e0de7f5df31 Durgadoss R     2011-05-20  162  	mutex_lock(&tdata->update_lock);
> bebe467823c0d8 Rudolf Marek    2007-05-08  163  
> 199e0de7f5df31 Durgadoss R     2011-05-20  164  	/* Check whether the time interval has elapsed */
> 199e0de7f5df31 Durgadoss R     2011-05-20  165  	if (!tdata->valid || time_after(jiffies, tdata->last_updated + HZ)) {
> e78264610cd902 Marcelo Tosatti 2022-12-15  166  		if (!housekeeping_cpu(tdata->cpu, HK_TYPE_MISC))
> e78264610cd902 Marcelo Tosatti 2022-12-15  167  			return -EINVAL;
> 
> mutex_unlock(&tdata->update_lock);
> 
> 199e0de7f5df31 Durgadoss R     2011-05-20  168  		rdmsr_on_cpu(tdata->cpu, tdata->status_reg, &eax, &edx);
> bf6ea084ebb54c Guenter Roeck   2013-11-20  169  		/*
> bf6ea084ebb54c Guenter Roeck   2013-11-20  170  		 * Ignore the valid bit. In all observed cases the register
> bf6ea084ebb54c Guenter Roeck   2013-11-20  171  		 * value is either low or zero if the valid bit is 0.
> bf6ea084ebb54c Guenter Roeck   2013-11-20  172  		 * Return it instead of reporting an error which doesn't
> bf6ea084ebb54c Guenter Roeck   2013-11-20  173  		 * really help at all.
> bf6ea084ebb54c Guenter Roeck   2013-11-20  174  		 */
> bf6ea084ebb54c Guenter Roeck   2013-11-20  175  		tdata->temp = tdata->tjmax - ((eax >> 16) & 0x7f) * 1000;
> 952a11ca32a604 Paul Fertser    2021-09-24  176  		tdata->valid = true;
> 199e0de7f5df31 Durgadoss R     2011-05-20  177  		tdata->last_updated = jiffies;
> bebe467823c0d8 Rudolf Marek    2007-05-08  178  	}
> bebe467823c0d8 Rudolf Marek    2007-05-08  179  
> 199e0de7f5df31 Durgadoss R     2011-05-20  180  	mutex_unlock(&tdata->update_lock);
> bf6ea084ebb54c Guenter Roeck   2013-11-20 @181  	return sprintf(buf, "%d\n", tdata->temp);
> bebe467823c0d8 Rudolf Marek    2007-05-08  182  }
> 
> -- 
> 0-DAY CI Kernel Test Service
> https://01.org/lkp

Thanks,

v3 of the patch should not suffer from this issue.