linux-kernel - Re: Bug: d0e936adbd22 crashes at boot

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Date:   Fri, 03 Sep 2021 07:13:16 -0700
From:   Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:     Jens Axboe <axboe@...nel.dk>, LKML <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Len Brown <lenb@...nel.org>, inux-pm@...r.kernel.org
Subject: Re: Bug: d0e936adbd22 crashes at boot

Hi Axboe,

Thanks for reporting.
On Fri, 2021-09-03 at 07:36 -0600, Jens Axboe wrote:
> Hi,
> 
> Booting Linus's tree causes a crash on my laptop, an x1 gen9. This was
> a bit
> difficult to pin down as it crashes before the display is up, but I
> managed
> to narrow it down to:
> 
> commit d0e936adbd2250cb03f2e840c6651d18edc22ace
> Author: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Date:   Thu Aug 19 19:40:06 2021 -0700
> 
>     cpufreq: intel_pstate: Process HWP Guaranteed change notification
> 
> which crashes with a NULL pointer deref in notify_hwp_interrupt() ->
> queue_delayed_work_on().
> 
> Reverting this change makes the laptop boot fine again.
> 
Does this change fixes your issue?

diff --git a/drivers/cpufreq/intel_pstate.c
b/drivers/cpufreq/intel_pstate.c
index b4ffe6c8a0d0..6a3c6f60ad12 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -1650,7 +1650,10 @@ void notify_hwp_interrupt(void)
                return;
 
        cpudata = all_cpu_data[this_cpu];
-       schedule_delayed_work_on(this_cpu, &cpudata->hwp_notify_work,
msecs_to_jiffies(10));
+       if (cpudata)
+               schedule_delayed_work_on(this_cpu, &cpudata-
>hwp_notify_work, msecs_to_jiffies(10));
+       else
+               wrmsrl(MSR_HWP_STATUS, 0);
 }
 
 static void intel_pstate_enable_hwp_interrupt(struct cpudata *cpudata)


Thanks,
Srinivas