The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From de002c55cadfc2f6cdf0ed427526f6085d240238 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" rafael.j.wysocki@intel.com Date: Tue, 28 Jul 2020 19:09:32 +0200 Subject: [PATCH] cpufreq: intel_pstate: Fix EPP setting via sysfs in active mode
Because intel_pstate_set_energy_pref_index() reads and writes the MSR_HWP_REQUEST register without using the cached value of it used by intel_pstate_hwp_boost_up() and intel_pstate_hwp_boost_down(), those functions may overwrite the value written by it and so the EPP value set via sysfs may be lost.
To avoid that, make intel_pstate_set_energy_pref_index() take the cached value of MSR_HWP_REQUEST just like the other two routines mentioned above and update it with the new EPP value coming from user space in addition to updating the MSR.
Note that the MSR itself still needs to be updated too in case hwp_boost is unset or the boosting mechanism is not active at the EPP change time.
Fixes: e0efd5be63e8 ("cpufreq: intel_pstate: Add HWP boost utility and sched util hooks") Reported-by: Francisco Jerez currojerez@riseup.net Cc: 4.18+ stable@vger.kernel.org # 4.18+: 3da97d4db8ee cpufreq: intel_pstate: Rearrange ... Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Reviewed-by: Francisco Jerez currojerez@riseup.net
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index c55f6e35a1e3..7f5d81931483 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -650,11 +650,12 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, epp = cpu_data->epp_default;
if (boot_cpu_has(X86_FEATURE_HWP_EPP)) { - u64 value; - - ret = rdmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, &value); - if (ret) - return ret; + /* + * Use the cached HWP Request MSR value, because the register + * itself may be updated by intel_pstate_hwp_boost_up() or + * intel_pstate_hwp_boost_down() at any time. + */ + u64 value = READ_ONCE(cpu_data->hwp_req_cached);
value &= ~GENMASK_ULL(31, 24);
@@ -664,6 +665,12 @@ static int intel_pstate_set_energy_pref_index(struct cpudata *cpu_data, epp = epp_values[pref_index - 1];
value |= (u64)epp << 24; + /* + * The only other updater of hwp_req_cached in the active mode, + * intel_pstate_hwp_set(), is called under the same lock as this + * function, so it cannot run in parallel with the update below. + */ + WRITE_ONCE(cpu_data->hwp_req_cached, value); ret = wrmsrl_on_cpu(cpu_data->cpu, MSR_HWP_REQUEST, value); } else { if (epp == -EINVAL)