Re: [REGRESSION] Intel Turbo Boost stuck disabled on some Clevo machines (was: [PATCH] cpufreq: intel_pstate: Unchecked MSR aceess in legacy mode)

srinivas pandruvada
2025-09-10T17:15:11Z

On Wed, 2025-09-10 at 11:36 -0500, Aaron Rainbolt wrote:
> On Wed, 30 Apr 2025 16:29:09 +0200
> "Rafael J. Wysocki" <rafael@kernel.org> wrote:
>
> > On Tue, Apr 29, 2025 at 11:07 PM Srinivas Pandruvada
> > <srinivas.pandruvada@linux.intel.com> wrote:
> > >
> > > When turbo mode is unavailable on a Skylake-X system, executing
> > > the
> > > command:
> > > "echo 1 > /sys/devices/system/cpu/intel_pstate/no_turbo"
> > > results in an unchecked MSR access error: WRMSR to 0x199
> > > (attempted to write 0x0000000100001300).
> > >
> > > This issue was reproduced on an OEM (Original Equipment
> > > Manufacturer) system and is not a common problem across all
> > > Skylake-X systems.
> > >
> > > This error occurs because the MSR 0x199 Turbo Engage Bit (bit 32)
> > > is set when turbo mode is disabled. The issue arises when
> > > intel_pstate fails to detect that turbo mode is disabled. Here
> > > intel_pstate relies on MSR_IA32_MISC_ENABLE bit 38 to determine
> > > the
> > > status of turbo mode. However, on this system, bit 38 is not set
> > > even when turbo mode is disabled.
> > >
> > > According to the Intel Software Developer's Manual (SDM), the
> > > BIOS
> > > sets this bit during platform initialization to enable or disable
> > > opportunistic processor performance operations. Logically, this
> > > bit
> > > should be set in such cases. However, the SDM also specifies that
> > > "OS and applications must use CPUID leaf 06H to detect processors
> > > with opportunistic processor performance operations enabled."
> > >
> > > Therefore, in addition to checking MSR_IA32_MISC_ENABLE bit 38,
> > > verify that CPUID.06H:EAX[1] is 0 to accurately determine if
> > > turbo
> > > mode is disabled.
> > >
> > > Fixes: 4521e1a0ce17 ("cpufreq: intel_pstate: Reflect current
> > > no_turbo state correctly") Signed-off-by: Srinivas Pandruvada
> > > <srinivas.pandruvada@linux.intel.com> Cc: stable@vger.kernel.org
> > > ---
> > >  drivers/cpufreq/intel_pstate.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/cpufreq/intel_pstate.c
> > > b/drivers/cpufreq/intel_pstate.c index f41ed0b9e610..ba9bf06f1c77
> > > 100644 --- a/drivers/cpufreq/intel_pstate.c
> > > +++ b/drivers/cpufreq/intel_pstate.c
> > > @@ -598,6 +598,9 @@ static bool turbo_is_disabled(void)
> > >  {
> > >         u64 misc_en;
> > >
> > > +       if (!cpu_feature_enabled(X86_FEATURE_IDA))
> > > +               return true;
> > > +
> > >         rdmsrl(MSR_IA32_MISC_ENABLE, misc_en);
> > >
> > >         return !!(misc_en & MSR_IA32_MISC_ENABLE_TURBO_DISABLE);
> > > --
> >
> > Applied as a fix for 6.15-rc, thanks!
> >
>
> FYI, this seems to have broken turbo boost on some Clevo systems with
> an Intel Core i9-14900HX CPU. These CPUs obviously support turbo
> boost,
> and kernels without this commit have turbo boost working properly,
> but
> after this commit turbo boost is stuck disabled and cannot be
> enabled by writing to /sys/devices/system/cpu/intel_pstate/no_turbo.
> I
> made a bug report about this against Ubuntu's kernel at [1], which is
> the only report I know that is able to point to this commit as having
> broken things. However, it looks like an Arch Linux user [2] and a
> Gentoo user [3] are running into the same thing.
>

As the bug report suggested, the system boots with no turbo, it must be
forcefully turned ON by writing to this attribute.
I wonder if there is a BIOS option to turn ON turbo on this system?

This processor itself is capable of up to 5.8 GHz turbo.

I will try to find contact at Clevo.

We can try to reduce scope of this change to non HWP only where there
is unchecked MSR issue.

Thanks,
Srinivas

> [1]
> https://bugs.launchpad.net/ubuntu/+source/linux-hwe-6.14/+bug/2122531
>
> [2] https://bbs.archlinux.org/viewtopic.php?id=305564
>
> [3]
> https://forums.gentoo.org/viewtopic-p-8866128.html?sid=e97619cff0d9c79c2eea2cfe8f60b0d3