linux-kernel - Re: [PATCH] cpufreq: intel_pstate: Fix unchecked MSR 0x773 access

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Date:   Thu, 4 Nov 2021 19:51:21 +0100
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Len Brown <lenb@...nel.org>
Subject: Re: [PATCH] cpufreq: intel_pstate: Fix unchecked MSR 0x773 access

On Thu, Nov 4, 2021 at 3:17 PM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> On Thu, 2021-11-04 at 09:30 -0400, Steven Rostedt wrote:
> > On Wed,  3 Nov 2021 22:19:25 -0700
> > Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote:
> >
> > > It is possible that on some platforms HWP interrupts are disabled.
> > > In
> > > that case accessing MSR 0x773 will result in warning.
> > >
> > > So check X86_FEATURE_HWP_NOTIFY feature to access MSR 0x773. The
> > > other
> > > places in code where this MSR is accessed, already checks this
> > > feature
> > > except during disable path called during cpufreq offline and
> > > suspend
> > > callbacks.
> > >
> > > Fixes: 57577c996d73 ("cpufreq: intel_pstate: Process HWP Guaranteed
> > > change notification")
> > > Reported-by: Steven Rostedt <rostedt@...dmis.org>
> >
> > I added this patch on top of the above commit and I verified that the
> > issue
> > goes away. And just to confirm, I removed the patch, and the issue
> > reappeared.
> >
> > Tested-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
> >
> Thanks for the test.
> Sorry again for the mess up.
>
> -Srinivas
>
> > -- Steve
> >
> >
> > > Signed-off-by: Srinivas Pandruvada <
> > > srinivas.pandruvada@...ux.intel.com>
> > > ---
> > >  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 349ddbaef796..1e6898dc76b6 100644
> > > --- a/drivers/cpufreq/intel_pstate.c
> > > +++ b/drivers/cpufreq/intel_pstate.c
> > > @@ -1620,6 +1620,9 @@ static void
> > > intel_pstate_disable_hwp_interrupt(struct cpudata *cpudata)
> > >  {
> > >         unsigned long flags;
> > >
> > > +       if (!boot_cpu_has(X86_FEATURE_HWP_NOTIFY))
> > > +               return;
> > > +
> > >         /* wrmsrl_on_cpu has to be outside spinlock as this can
> > > result in IPC */
> > >         wrmsrl_on_cpu(cpudata->cpu, MSR_HWP_INTERRUPT, 0x00);
> > >

Applied as 5.16-rc material, thanks!