linux-kernel - Re: [PATCH 2/5] perf, x86, uncore: Add Haswell-EP uncore support

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Date:	Mon, 27 Oct 2014 13:13:48 -0700
From:	Alexei Starovoitov <alexei.starovoitov@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Stephane Eranian <eranian@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Yan, Zheng" <zheng.z.yan@...el.com>
Subject: Re: [PATCH 2/5] perf, x86, uncore: Add Haswell-EP uncore support

On Mon, Oct 27, 2014 at 4:57 AM, Andi Kleen <andi@...stfloor.org> wrote:
> Alexei Starovoitov <alexei.starovoitov@...il.com> writes:
>> my E5-1630 v3 crashes hard during boot in
>> snbep_uncore_msr_init_box()+0x3c
>
>> I don't have a setup to capture the screen so early in the boot.
>> So this is just heads up.
>
> Is it a general general protection fault or a page fault?
>
> If it's a page fault please post the disassembled code:
>
> gdb vmlinux
> disassemble  snbep_uncore_msr_init_box
>

snbep_uncore_msr_init_box() is called with:
[    1.055678] msr 0
[    1.056027] msr 3584
[    1.056376] msr 3600
[    1.056725] msr 3616
[    1.057074] msr 3632
[    1.057424] msr 1824
[    1.057773] msr 1834
[    1.058123] msr 1844
[    1.058473] msr 1854
[    1.058822] msr 1808

since msr 3584 is HSWEP_C0_MSR_PMON_BOX_CTL
I've tried the following workaround which helped as well:
diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore_snbep.c
b/arch/x86/kernel/cpu/perf_event_intel_uncore_snbep.c
index adf138eac85c..1ca46523a541 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore_snbep.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore_snbep.c
@@ -368,7 +368,7 @@ static void snbep_uncore_msr_init_box(struct
intel_uncore_box *box)
 {
        unsigned msr = uncore_msr_box_ctl(box);

-       if (msr)
+       if (msr && msr >= 3584)
                wrmsrl(msr, SNBEP_PMON_BOX_CTL_INT);
 }
--
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