Messages in this thread | | | Date | Thu, 15 Dec 2022 06:22:16 -0800 | From | Guenter Roeck <> | Subject | Re: [PATCH] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs |
| |
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
| |