Re: intel_pstate_get_hwp_cap on wrong CPU

[srinivas pandruvada <srinivas.pandruvada@linux.intel.com>]

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Hi Sebastian,


On Wed, 2024-05-29 at 17:57 +0200, Sebastian Andrzej Siewior wrote:
> Hi,
> 
> this just popped up:
> > [ 6538.614568] unchecked MSR access error: RDMSR from 0x771 at rIP:

Please check if the attached change fixes?

Thanks,
Srinivas


> > 0xffffffff817d2250 (__rdmsr_on_cpu+0x20/0x50)
> > [ 6538.625714] Call Trace:
> > [ 6538.629156]  <TASK>
> > [ 6538.675067]  generic_exec_single+0x58/0x120
> > [ 6538.680236]  smp_call_function_single+0xbf/0x110
> > [ 6538.696333]  rdmsrl_on_cpu+0x46/0x60
> > [ 6538.700894]  intel_pstate_get_hwp_cap+0x1b/0x70
> > [ 6538.706420]  intel_pstate_update_limits+0x2a/0x60
> > [ 6538.712110]  acpi_processor_notify+0xb7/0x140
> > [ 6538.717479]  acpi_ev_notify_dispatch+0x3b/0x60
> > [ 6538.722910]  acpi_os_execute_deferred+0xf/0x20
> > [ 6538.728346]  process_one_work+0x13d/0x350
> > [ 6538.733342]  worker_thread+0x2c2/0x3d0
> > [ 6538.743066]  kthread+0xca/0x100
> > [ 6538.751844]  ret_from_fork+0x2c/0x40
> > [ 6538.761073]  ret_from_fork_asm+0x11/0x20
> > [ 6538.765993]  </TASK>
> 
> > root@h:~# grep . /sys/devices/system/cpu/intel_pstate/*
> > /sys/devices/system/cpu/intel_pstate/max_perf_pct:100
> > /sys/devices/system/cpu/intel_pstate/min_perf_pct:36
> > /sys/devices/system/cpu/intel_pstate/no_turbo:0
> > /sys/devices/system/cpu/intel_pstate/num_pstates:4294967285
> ^ => -EAGAIN
> 
> > /sys/devices/system/cpu/intel_pstate/status:passive
> > /sys/devices/system/cpu/intel_pstate/turbo_pct:0
> 
> > # cpupower frequency-info
> > analyzing CPU 0:
> >  driver: intel_cpufreq
> …
> 
> from turbostat:
> > CPUID(0): GenuineIntel 0xf CPUID levels
> > CPUID(1): family:model:stepping 0x6:3f:4 (6:63:4) microcode 0x1a
> > CPUID(0x80000000): max_extended_levels: 0x80000008
> > CPUID(1): SSE3 MONITOR SMX EIST TM2 TSC MSR ACPI-TM HT TM
> > CPUID(6): APERF, TURBO, DTS, PTM, No-HWP, No-HWPnotify, No-
> > HWPwindow, No-HWPepp, No-HWPpkg, EPB
> > cpu4: MSR_IA32_MISC_ENABLE: 0x00850089 (TCC EIST MWAIT PREFETCH
> > TURBO)
> > CPUID(7): No-SGX No-Hybrid
> 
> This is v6.10.0-rc1.
> 
> Sebastian
> 


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From f85a83508ef029bceaf9192cb648d66f32b61d02 Mon Sep 17 00:00:00 2001
From: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Date: Wed, 29 May 2024 15:30:49 -0700
Subject: [PATCH] cpufreq: intel_pstate: Fix unchecked HWP MSR access

HWP MSR 0x771 can be only read on a CPU which supports HWP and enabled.
Hence intel_pstate_get_hwp_cap() can only be called when hwp_active is
true.

Reported-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Closes: https://lore.kernel.org/linux-pm/20240529155740.Hq2Hw7be@linutronix.de/
Fixes: e8217b4bece3 ("cpufreq: intel_pstate: Update the maximum CPU frequency consistently")
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
---
 drivers/cpufreq/intel_pstate.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 4b986c044741..65d3f79104bd 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1153,7 +1153,8 @@ static void intel_pstate_update_policies(void)
 static void __intel_pstate_update_max_freq(struct cpudata *cpudata,
 					   struct cpufreq_policy *policy)
 {
-	intel_pstate_get_hwp_cap(cpudata);
+	if (hwp_active)
+		intel_pstate_get_hwp_cap(cpudata);
 
 	policy->cpuinfo.max_freq = READ_ONCE(global.no_turbo) ?
 			cpudata->pstate.max_freq : cpudata->pstate.turbo_freq;
-- 
2.25.1