On Tuesday, December 24, 2013 09:36:01 PM Viresh Kumar wrote:
> Adding Dirk..
>
> On 24 December 2013 20:06, Josh Boyer <jwboyer@xxxxxxxxxxxxxxxxx> wrote:
> > Hi All,
> >
> > We've had a report [1] that the pstate driver causes KVM guests to
> > fail to boot because of a divide error. See the backtrace below.
> >
> > 4.839784] Intel P-state driver initializing.
> > [ 4.859972] Intel pstate controlling: cpu 0
> > [ 4.867653] cpufreq: __cpufreq_add_dev: ->get() failed
>
> After a call to ->init(), ->get() is supposed to work.
> @Dirk: Any idea why it failed?
Well, it looks like sample->freq is 0 in intel_pstate_get().
> And then I don't know what made this divide by zero to happen :)
>From code inspection it looks like that is caused by the
intel_pstate_get_scaled_busy() called from intel_pstate_adjust_busy_pstate(),
so it appears that cpu->pstate.current_state is 0 at that point.
I'm wondering if something like the (untested) patch below helps, then?
Rafael
---
drivers/cpufreq/intel_pstate.c | 5 +++++
1 file changed, 5 insertions(+)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -652,6 +652,11 @@ static int intel_pstate_init_cpu(unsigne
cpu = all_cpu_data[cpunum];
intel_pstate_get_cpu_pstates(cpu);
+ if (!cpu->pstate.current_state) {
+ all_cpu_data[cpunum] = NULL;
+ kfree(cpu);
+ return -ENODATA;
+ }
cpu->cpu = cpunum;
--
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