RE: [PATCH v7 3/6] cpufreq: amd-pstate: implement cpb_boost sysfs entry for boost control

[Yuan, Perry]

[AMD Official Use Only - General]

Hi Mario


> -----Original Message-----
> From: Limonciello, Mario <Mario.Limonciello@xxxxxxx>
> Sent: Friday, April 26, 2024 5:17 AM
> To: Yuan, Perry <Perry.Yuan@xxxxxxx>; rafael.j.wysocki@xxxxxxxxx;
> viresh.kumar@xxxxxxxxxx; Shenoy, Gautham Ranjal
> <gautham.shenoy@xxxxxxx>; Petkov, Borislav <Borislav.Petkov@xxxxxxx>;
> Huang, Ray <Ray.Huang@xxxxxxx>; Deucher, Alexander
> <Alexander.Deucher@xxxxxxx>
> Cc: Huang, Shimmer <Shimmer.Huang@xxxxxxx>; oleksandr@xxxxxxxxxxxxxx;
> Du, Xiaojian <Xiaojian.Du@xxxxxxx>; Meng, Li (Jassmine)
> <Li.Meng@xxxxxxx>; linux-pm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v7 3/6] cpufreq: amd-pstate: implement cpb_boost sysfs
> entry for boost control
>
> On 4/23/2024 03:40, Perry Yuan wrote:
> > From: Perry Yuan <Perry.Yuan@xxxxxxx>
> >
> > With this new sysfs entry `cpb_boost`created, user can change CPU
> > boost state dynamically under `active`, `guided` and `passive` modes.
> > And the highest perf and frequency will also be updated as the boost
> > state changing.
> >
> > 0): check current boost state
> > cat /sys/devices/system/cpu/amd_pstate/cpb_boost
> >
> > 1): disable CPU boost
> > sudo bash -c "echo 0 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> >
> > 2): enable CPU boost
> > sudo bash -c "echo 1 > /sys/devices/system/cpu/amd_pstate/cpb_boost"
> >
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217931
> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=217618
> > Signed-off-by: Perry Yuan <Perry.Yuan@xxxxxxx>
> > ---
> >   drivers/cpufreq/amd-pstate.c | 99
> ++++++++++++++++++++++++++++++++++++
> >   1 file changed, 99 insertions(+)
> >
> > diff --git a/drivers/cpufreq/amd-pstate.c
> > b/drivers/cpufreq/amd-pstate.c index 3d86cd7c9073..49eeb38fcf20 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -1291,6 +1291,103 @@ static ssize_t prefcore_show(struct device *dev,
> >     return sysfs_emit(buf, "%s\n",
> str_enabled_disabled(amd_pstate_prefcore));
> >   }
> >
> > +static int amd_cpu_boost_update(struct amd_cpudata *cpudata, u32 on)
> > +{
> > +   struct cpufreq_policy *policy = cpufreq_cpu_acquire(cpudata->cpu);
> > +   struct cppc_perf_ctrls perf_ctrls;
> > +   u32 highest_perf, nominal_perf, nominal_freq, max_freq;
> > +   int ret;
> > +
> > +   if (!policy)
> > +           return -ENODATA;
> > +
> > +   highest_perf = READ_ONCE(cpudata->highest_perf);
> > +   nominal_perf = READ_ONCE(cpudata->nominal_perf);
> > +   nominal_freq = READ_ONCE(cpudata->nominal_freq);
> > +   max_freq = READ_ONCE(cpudata->max_freq);
> > +
> > +   if (boot_cpu_has(X86_FEATURE_CPPC)) {
> > +           u64 value = READ_ONCE(cpudata->cppc_req_cached);
> > +
> > +           value &= ~GENMASK_ULL(7, 0);
> > +           value |= on ? highest_perf : nominal_perf;
> > +           WRITE_ONCE(cpudata->cppc_req_cached, value);
> > +
> > +           wrmsrl_on_cpu(cpudata->cpu, MSR_AMD_CPPC_REQ, value);
> > +
> > +   } else {
> > +           perf_ctrls.max_perf = on ? highest_perf : nominal_perf;
> > +           ret = cppc_set_epp_perf(cpudata->cpu, &perf_ctrls, 1);
> > +           if (ret) {
> > +                   pr_debug("failed to set energy perf value (%d)\n", ret);
> > +                   return ret;
> > +           }
> > +   }
> > +
> > +   if (on)
> > +           policy->cpuinfo.max_freq = max_freq;
> > +   else
> > +           policy->cpuinfo.max_freq = nominal_freq;
> > +
> > +   policy->max = policy->cpuinfo.max_freq;
> > +
> > +   if (cppc_state == AMD_PSTATE_PASSIVE) {
> > +           ret = freq_qos_update_request(&cpudata->req[1],
> > +                                 policy->cpuinfo.max_freq);
> > +   }
> > +
> > +   cpufreq_cpu_release(policy);
> > +
> > +   return ret;
> > +}
> > +
> > +static ssize_t cpb_boost_show(struct device *dev,
> > +                      struct device_attribute *attr, char *buf) {
> > +   return sysfs_emit(buf, "%u\n", amd_pstate_global_params.cpb_boost);
> > +}
> > +
> > +static ssize_t cpb_boost_store(struct device *dev, struct device_attribute *b,
> > +                       const char *buf, size_t count) {
> > +   bool new_state;
> > +   ssize_t ret;
> > +   int cpu;
> > +
> > +   mutex_lock(&amd_pstate_driver_lock);
>
> This mutex lock should be after the check for cpb_supported and kstrtobool
> check.  Right now you have two cases that the lock doesn't get released.

Yes, the issue has been resolved by v8.
I have made one new version addressing the feedback from you and Ray
https://lore.kernel.org/lkml/cover.1714112854.git.perry.yuan@xxxxxxx/
Please help to take a look.

Thank you.

Perry.


>
> > +   if (!amd_pstate_global_params.cpb_supported) {
> > +           pr_err("Boost mode is not supported by this processor or
> SBIOS\n");
> > +           return -EINVAL;
> > +   }
> > +
> > +   ret = kstrtobool(buf, &new_state);
> > +   if (ret)
> > +           return -EINVAL;
> > +
> > +   amd_pstate_global_params.cpb_boost = !!new_state;
> > +
> > +   for_each_present_cpu(cpu) {
> > +
> > +           struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
> > +           struct amd_cpudata *cpudata = policy->driver_data;
> > +
> > +           if (!cpudata) {
> > +                   pr_err("cpudata is NULL\n");
> > +                   ret = -ENODATA;
> > +                   cpufreq_cpu_put(policy);
> > +                   goto err_exit;
> > +           }
> > +
> > +           amd_cpu_boost_update(cpudata,
> amd_pstate_global_params.cpb_boost);
> > +           refresh_frequency_limits(policy);
> > +           cpufreq_cpu_put(policy);
> > +   }
> > +
> > +err_exit:
> > +   mutex_unlock(&amd_pstate_driver_lock);
> > +   return ret < 0 ? ret : count;
> > +}
> > +
> >   cpufreq_freq_attr_ro(amd_pstate_max_freq);
> >   cpufreq_freq_attr_ro(amd_pstate_lowest_nonlinear_freq);
> >
> > @@ -1301,6 +1398,7 @@
> cpufreq_freq_attr_rw(energy_performance_preference);
> >   cpufreq_freq_attr_ro(energy_performance_available_preferences);
> >   static DEVICE_ATTR_RW(status);
> >   static DEVICE_ATTR_RO(prefcore);
> > +static DEVICE_ATTR_RW(cpb_boost);
> >
> >   static struct freq_attr *amd_pstate_attr[] = {
> >     &amd_pstate_max_freq,
> > @@ -1325,6 +1423,7 @@ static struct freq_attr *amd_pstate_epp_attr[] = {
> >   static struct attribute *pstate_global_attributes[] = {
> >     &dev_attr_status.attr,
> >     &dev_attr_prefcore.attr,
> > +   &dev_attr_cpb_boost.attr,
> >     NULL
> >   };
> >