From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
To: rjw@rjwysocki.net, viresh.kumar@linaro.org
Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, cai@lca.pw
Subject: [PATCH] cpufreq: intel_pstate: Fix Invalid EPB setting
Date: Thu, 31 Oct 2019 12:26:20 -0700 [thread overview]
Message-ID: <20191031192620.23482-1-srinivas.pandruvada@linux.intel.com> (raw)
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);
}
--
2.17.2
next reply other threads:[~2019-10-31 19:26 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-31 19:26 Srinivas Pandruvada [this message]
2019-11-04 11:28 ` [PATCH] cpufreq: intel_pstate: Fix Invalid EPB setting Rafael J. Wysocki
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