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Date: Thu, 6 Feb 2014 21:38:03 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Mark Davies <junk@...af.co.uk>
Cc: Vince Weaver <vince@...ter.net>, alan@...rguk.ukuu.org.uk,
Ingo Molnar <mingo@...nel.org>,
Stephane Eranian <eranian@...gle.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf,x86,p6: Add userspace RDPMC quirk for P6
On Thu, Feb 06, 2014 at 07:41:37PM +0000, Mark Davies wrote:
> Peter
>
> As I reported the problem I thought I better contribute by testing the
> fix.
>
> I took the patch below and managed to change the 3.4.78 code to match
> and tried to boot my Pentium Pro system but it hung as before. After
> some investigation I discovered the quirk is not being run, in fact no
> quirks were being run in init_hw_perf_events as x86_pmu.quirks was NULL.
>
> The problem as far as I can see is that the quirk is added to x86_pmu in
> p6_pmu_init but then x86_pmu is reassigned at the end of that function
> (x86_pmu = p6_pmu) resetting x86_pmu.quirks to NULL.
Right so far.
> x86_pmu looks like
> it is reassigned again in intel_pmu_init to either core_pmu or intel_pmu
> after the call to p6_pmu_init so I am not sure which x86_pmu.quirks
> init_hw_perf_events tries to use.
Note how intel_pmu_init() does: return p6_pmu_init(), so it will never
get to the x86_pmu assignment for the ARCH_PERFMON drivers.
Yep, thanks for testing and you're (mostly) quite right.
We can do the copy early though, if we return -ENODEV nothing will end
up using the x86_pmu anyway, so it doesn't matter what lives in there.
---
Subject: perf,x86,p6: Add userspace RDPMC quirk for PPro
From: Peter Zijlstra <peterz@...radead.org>
Date: Wed, 5 Feb 2014 20:48:51 +0100
PPro machines can die hard when PCE gets enabled due to a CPU erratum.
The safe way it so disable it by default and keep it disabled.
See erratum 26 in:
http://download.intel.com/design/archives/processors/pro/docs/24268935.pdf
Cc: Alan Cox <alan@...rguk.ukuu.org.uk>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Vince Weaver <vince@...ter.net>
Reported-by: Mark Davies <junk@...af.co.uk>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
---
arch/x86/kernel/cpu/perf_event.c | 6 +++-
arch/x86/kernel/cpu/perf_event.h | 1
arch/x86/kernel/cpu/perf_event_p6.c | 48 ++++++++++++++++++++++++------------
3 files changed, 39 insertions(+), 16 deletions(-)
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -1521,6 +1521,8 @@ static int __init init_hw_perf_events(vo
pr_cont("%s PMU driver.\n", x86_pmu.name);
+ x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */
+
for (quirk = x86_pmu.quirks; quirk; quirk = quirk->next)
quirk->func();
@@ -1534,7 +1536,6 @@ static int __init init_hw_perf_events(vo
__EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_counters) - 1,
0, x86_pmu.num_counters, 0, 0);
- x86_pmu.attr_rdpmc = 1; /* enable userspace RDPMC usage by default */
x86_pmu_format_group.attrs = x86_pmu.format_attrs;
if (x86_pmu.event_attrs)
@@ -1820,6 +1821,9 @@ static ssize_t set_attr_rdpmc(struct dev
if (ret)
return ret;
+ if (x86_pmu.attr_rdpmc_broken)
+ return -ENOTSUPP;
+
if (!!val != !!x86_pmu.attr_rdpmc) {
x86_pmu.attr_rdpmc = !!val;
smp_call_function(change_rdpmc, (void *)val, 1);
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -409,6 +409,7 @@ struct x86_pmu {
/*
* sysfs attrs
*/
+ int attr_rdpmc_broken;
int attr_rdpmc;
struct attribute **format_attrs;
struct attribute **event_attrs;
--- a/arch/x86/kernel/cpu/perf_event_p6.c
+++ b/arch/x86/kernel/cpu/perf_event_p6.c
@@ -231,31 +231,49 @@ static __initconst const struct x86_pmu
};
+static __init void p6_pmu_rdpmc_quirk(void)
+{
+ if (boot_cpu_data.x86_mask < 9) {
+ /*
+ * PPro erratum 26; fixed in stepping 9 and above.
+ */
+ pr_warn("Userspace RDPMC support disabled due to a CPU erratum\n");
+ x86_pmu.attr_rdpmc_broken = 1;
+ x86_pmu.attr_rdpmc = 0;
+ }
+}
+
__init int p6_pmu_init(void)
{
+ x86_pmu = p6_pmu;
+
switch (boot_cpu_data.x86_model) {
- case 1:
- case 3: /* Pentium Pro */
- case 5:
- case 6: /* Pentium II */
- case 7:
- case 8:
- case 11: /* Pentium III */
- case 9:
- case 13:
- /* Pentium M */
+ case 1: /* Pentium Pro */
+ x86_add_quirk(p6_pmu_rdpmc_quirk);
+ break;
+
+ case 3: /* Pentium II - Klamath */
+ case 5: /* Pentium II - Deschutes */
+ case 6: /* Pentium II - Mendocino */
break;
+
+ case 7: /* Pentium III - Katmai */
+ case 8: /* Pentium III - Coppermine */
+ case 10: /* Pentium III Xeon */
+ case 11: /* Pentium III - Tualatin */
+ break;
+
+ case 9: /* Pentium M - Banias */
+ case 13: /* Pentium M - Dothan */
+ break;
+
default:
- pr_cont("unsupported p6 CPU model %d ",
- boot_cpu_data.x86_model);
+ pr_cont("unsupported p6 CPU model %d ", boot_cpu_data.x86_model);
return -ENODEV;
}
- x86_pmu = p6_pmu;
-
memcpy(hw_cache_event_ids, p6_hw_cache_event_ids,
sizeof(hw_cache_event_ids));
-
return 0;
}
--
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