| Message ID | 20191031192620.23482-1-srinivas.pandruvada@linux.intel.com (mailing list archive) |
|---|---|
| State | Mainlined, archived |
| Headers | show |
| Series | cpufreq: intel_pstate: Fix Invalid EPB setting | expand |
On Thursday, October 31, 2019 8:26:20 PM CET Srinivas Pandruvada wrote: > The max value of EPB can be only be 0x0F. Setting more than that results > in "unchecked MSR access error". During CPU offline via cpufreq stop_cpu() > callback, this error condition is triggered in the function > intel_pstate_hwp_force_min_perf(). > > Instead, EPB corresponding to preference to maximize energy saving (0x0F), > can be set. But this will conflict with the save/restore done in > arch/x86/kernel/cpu/intel_epb.c. Based on the test, if 0x0F is set in the > function intel_pstate_hwp_force_min_perf(), this gets restored during next > CPU online operation. This is not desired. > > Hence don't set EPB in the offline path in this driver and let the > processing in intel_epb.c handle EPB. > > Fixes: af3b7379e2d70 ("cpufreq: intel_pstate: Force HWP min perf before offline") > Reported-by: Qian Cai <cai@lca.pw> > Cc: 5.0+ <stable@vger.kernel.org> # 5.0+ > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> > --- > drivers/cpufreq/intel_pstate.c | 4 +--- > 1 file changed, 1 insertion(+), 3 deletions(-) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index 53a51c169451..8ab31702cf6a 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -847,11 +847,9 @@ static void intel_pstate_hwp_force_min_perf(int cpu) > value |= HWP_MAX_PERF(min_perf); > value |= HWP_MIN_PERF(min_perf); > > - /* Set EPP/EPB to min */ > + /* Set EPP to min */ > if (boot_cpu_has(X86_FEATURE_HWP_EPP)) > value |= HWP_ENERGY_PERF_PREFERENCE(HWP_EPP_POWERSAVE); > - else > - intel_pstate_set_epb(cpu, HWP_EPP_BALANCE_POWERSAVE); > > wrmsrl_on_cpu(cpu, MSR_HWP_REQUEST, value); > } > Applying as a fix for 5.4, thanks!
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 53a51c169451..8ab31702cf6a 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -847,11 +847,9 @@ static void intel_pstate_hwp_force_min_perf(int cpu) value |= HWP_MAX_PERF(min_perf); value |= HWP_MIN_PERF(min_perf); - /* Set EPP/EPB to min */ + /* Set EPP to min */ if (boot_cpu_has(X86_FEATURE_HWP_EPP)) value |= HWP_ENERGY_PERF_PREFERENCE(HWP_EPP_POWERSAVE); - else - intel_pstate_set_epb(cpu, HWP_EPP_BALANCE_POWERSAVE); wrmsrl_on_cpu(cpu, MSR_HWP_REQUEST, value); }
The max value of EPB can be only be 0x0F. Setting more than that results in "unchecked MSR access error". During CPU offline via cpufreq stop_cpu() callback, this error condition is triggered in the function intel_pstate_hwp_force_min_perf(). Instead, EPB corresponding to preference to maximize energy saving (0x0F), can be set. But this will conflict with the save/restore done in arch/x86/kernel/cpu/intel_epb.c. Based on the test, if 0x0F is set in the function intel_pstate_hwp_force_min_perf(), this gets restored during next CPU online operation. This is not desired. Hence don't set EPB in the offline path in this driver and let the processing in intel_epb.c handle EPB. Fixes: af3b7379e2d70 ("cpufreq: intel_pstate: Force HWP min perf before offline") Reported-by: Qian Cai <cai@lca.pw> Cc: 5.0+ <stable@vger.kernel.org> # 5.0+ Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> --- drivers/cpufreq/intel_pstate.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)