Re: [Xen-devel] [PATCH] perf: Check all MSRs before passing hw check

[George Dunlap <george.dunlap@xxxxxxxxxxxxx>]

On 15/03/13 12:50, Jan Beulich wrote:
> > > > On 15.03.13 at 13:20, George Dunlap <george.dunlap@xxxxxxxxxxxxx> wrote:
> > --- a/arch/x86/kernel/cpu/perf_event.c
> > +++ b/arch/x86/kernel/cpu/perf_event.c
> > @@ -182,6 +182,7 @@ static bool check_hw_exists(void)
> >   {
> >         u64 val, val_new = ~0;
> >         int i, reg, ret = 0;
> > +       int bios_fail = 0;
> >   
> >   	/*
> >          * Check to see if the BIOS enabled any of the counters, if so
> > @@ -193,7 +194,7 @@ static bool check_hw_exists(void)
> >                 if (ret)
> >                         goto msr_fail;
> >                 if (val & ARCH_PERFMON_EVENTSEL_ENABLE)
> > -                       goto bios_fail;
> > +                       bios_fail = 1;
> >         }
> >   
> >   	if (x86_pmu.num_counters_fixed) {
> > @@ -203,7 +204,7 @@ static bool check_hw_exists(void)
> >                         goto msr_fail;
> >                 for (i = 0; i < x86_pmu.num_counters_fixed; i++) {
> >                         if (val & (0x03 << i*4))
> > -                               goto bios_fail;
> > +                               bios_fail = 1;
> >                 }
> >         }
> >   
> > @@ -221,14 +222,13 @@ static bool check_hw_exists(void)
> >         if (ret || val != val_new)
> >                 goto msr_fail;
> >   
> > -	return true;
> > -
> > -bios_fail:
> > -       /*
> > -        * We still allow the PMU driver to operate:
> > -        */
> > -       printk(KERN_CONT "Broken BIOS detected, complain to your hardware 
> > vendor.\n");
> > -       printk(KERN_ERR FW_BUG "the BIOS has corrupted hw-PMU resources (MSR %x is 
> > %Lx)\n", reg, val);
> > +       if (bios_fail) {
> > +               /*
> > +                * We still allow the PMU driver to operate:
> > +                */
> > +               printk(KERN_CONT "Broken BIOS detected, complain to your hardware 
> > vendor.\n");
> > +               printk(KERN_ERR FW_BUG "the BIOS has corrupted hw-PMU resources (MSR 
> > %x is %Lx)\n", reg, val);
> The values being printed here are not meaningful anymore with this
> patch.
Right -- then I guess the options are:
1. Don't print any values
2. Print values on the first broken MSR detected (but not subsequent ones)
3. Print values on all broken MSRs.

#2 is the current behavior, and won't risk spamming the console.

 -George


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