Messages in this thread | | | Date | Fri, 16 Dec 2022 09:56:20 -0800 | Subject | Re: [PATCH v2] hwmon: coretemp: avoid RDMSR interruptions to isolated CPUs | From | Guenter Roeck <> |
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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 > > > >
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