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Subject[PATCH 3/4] perf, x86: check ucode before disabling PEBS on SandyBridge v3
Date
From: Stephane Eranian <eranian@google.com>

[AK: Updated version of Stephane's patch, now using the new global
tracking microcode number and with the correct microcode revision
for SandyBridge-E*. Also use pr_warn_once and checkpatch fixes.]

This patch checks the microcode version before disabling
PEBS on SandyBridge model 42 (desktop, mobile), and 45 (SNB-EP).
PEBS was disabled for both models due to an erratum.

A workaround is implemented by micro-code 0x28. This patch checks
the microcode version and disables PEBS support if version < 0x28.
The check is done each time a PEBS event is created and NOT at boot
time because the micro-code update may only be done after the kernel
has booted.

Go to downloadcenter.intel.com to download microcode updates.
Need microcode update 6/6/2012 or later.

v2: Was Stephane's old revision
v3: Use boot_cpu_data.microcode (H. Peter Anvin)
Signed-off-by: Stephane Eranian <eranian@google.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event_intel.c | 37 +++++++++++++++++++++++--------
1 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 187c294..102d153 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -13,6 +13,7 @@

#include <asm/hardirq.h>
#include <asm/apic.h>
+#include <asm/processor.h>

#include "perf_event.h"

@@ -1392,6 +1393,25 @@ static void intel_pebs_aliases_snb(struct perf_event *event)
}
}

+static int check_pebs_quirks(void)
+{
+ int model = cpu_data(smp_processor_id()).x86_model;
+
+ /* do not have PEBS to begin with */
+ if (!x86_pmu.pebs)
+ return 0;
+
+ /*
+ * check ucode version for SNB, SNB-EP
+ */
+ if ((model == 42 && boot_cpu_data.microcode < 0x28) ||
+ (model == 45 && boot_cpu_data.microcode < 0x618)) {
+ pr_warn_once("SandyBridge PEBS unavailable due to CPU erratum, update microcode\n");
+ return -ENOTSUPP;
+ }
+ return 0;
+}
+
static int intel_pmu_hw_config(struct perf_event *event)
{
int ret = x86_pmu_hw_config(event);
@@ -1399,8 +1419,13 @@ static int intel_pmu_hw_config(struct perf_event *event)
if (ret)
return ret;

- if (event->attr.precise_ip && x86_pmu.pebs_aliases)
- x86_pmu.pebs_aliases(event);
+ if (event->attr.precise_ip) {
+ if (check_pebs_quirks())
+ return -ENOTSUPP;
+
+ if (x86_pmu.pebs_aliases)
+ x86_pmu.pebs_aliases(event);
+ }

if (intel_pmu_needs_lbr_smpl(event)) {
ret = intel_pmu_setup_lbr_filter(event);
@@ -1712,13 +1737,6 @@ static __init void intel_clovertown_quirk(void)
x86_pmu.pebs_constraints = NULL;
}

-static __init void intel_sandybridge_quirk(void)
-{
- printk(KERN_WARNING "PEBS disabled due to CPU errata.\n");
- x86_pmu.pebs = 0;
- x86_pmu.pebs_constraints = NULL;
-}
-
static const struct { int id; char *name; } intel_arch_events_map[] __initconst = {
{ PERF_COUNT_HW_CPU_CYCLES, "cpu cycles" },
{ PERF_COUNT_HW_INSTRUCTIONS, "instructions" },
@@ -1910,7 +1928,6 @@ __init int intel_pmu_init(void)

case 42: /* SandyBridge */
case 45: /* SandyBridge, "Romely-EP" */
- x86_add_quirk(intel_sandybridge_quirk);
case 58: /* IvyBridge */
memcpy(hw_cache_event_ids, snb_hw_cache_event_ids,
sizeof(hw_cache_event_ids));
--
1.7.7.6


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