diff mbox series

hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs

Message ID Y5sWMEG0xCl9bgEi@tpad
State New
Headers
Series hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs |

Commit Message

Marcelo Tosatti Dec. 15, 2022, 12:42 p.m. UTC 
  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>

Comments

Guenter Roeck Dec. 15, 2022, 2:22 p.m. UTC | #1 
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
Dan Carpenter Dec. 23, 2022, 10:48 a.m. UTC | #2 
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  }
Marcelo Tosatti Dec. 26, 2022, 12:43 p.m. UTC | #3 
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.
diff mbox series

Patch

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