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Subject[PATCH 11/14] perf, x86: Clean up IA32_PERF_CAPABILITIES usage
Saner PERF_CAPABILITIES support, which also exposes pebs_trap. Use that
latter to make PEBS's use of LBR conditional since a fault-like pebs
should already report the correct IP.

(As of this writing there is no known hardware that implements !pebs_trap)

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
---
arch/x86/kernel/cpu/perf_event.c | 15 ++++++++++++--
arch/x86/kernel/cpu/perf_event_intel.c | 10 +++++++++
arch/x86/kernel/cpu/perf_event_intel_ds.c | 30 ++++++++++++++---------------
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 18 +++--------------
4 files changed, 42 insertions(+), 31 deletions(-)
Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
@@ -154,6 +154,17 @@ struct cpu_hw_events {
#define for_each_event_constraint(e, c) \
for ((e) = (c); (e)->cmask; (e)++)

+union perf_capabilities {
+ struct {
+ u64 lbr_format : 6;
+ u64 pebs_trap : 1;
+ u64 pebs_arch_reg : 1;
+ u64 pebs_format : 4;
+ u64 smm_freeze : 1;
+ };
+ u64 capabilities;
+};
+
/*
* struct x86_pmu - generic x86 pmu
*/
@@ -190,7 +201,8 @@ struct x86_pmu {
/*
* Intel Arch Perfmon v2+
*/
- u64 intel_ctrl;
+ u64 intel_ctrl;
+ union perf_capabilities intel_cap;

/*
* Intel DebugStore bits
@@ -205,7 +217,6 @@ struct x86_pmu {
*/
unsigned long lbr_tos, lbr_from, lbr_to; /* MSR base regs */
int lbr_nr; /* hardware stack size */
- int lbr_format; /* hardware format */
};

static struct x86_pmu x86_pmu __read_mostly;
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel.c
@@ -834,6 +834,16 @@ static __init int intel_pmu_init(void)
if (version > 1)
x86_pmu.num_events_fixed = max((int)edx.split.num_events_fixed, 3);

+ /*
+ * v2 and above have a perf capabilities MSR
+ */
+ if (version > 1) {
+ u64 capabilities;
+
+ rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
+ x86_pmu.intel_cap.capabilities = capabilities;
+ }
+
intel_ds_init();

/*
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel_ds.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -342,7 +342,8 @@ static void intel_pmu_pebs_enable(struct
val |= 1ULL << hwc->idx;
wrmsrl(MSR_IA32_PEBS_ENABLE, val);

- intel_pmu_lbr_enable(event);
+ if (x86_pmu.intel_cap.pebs_trap)
+ intel_pmu_lbr_enable(event);
}

static void intel_pmu_pebs_disable(struct perf_event *event)
@@ -356,7 +357,8 @@ static void intel_pmu_pebs_disable(struc

hwc->config |= ARCH_PERFMON_EVENTSEL_INT;

- intel_pmu_lbr_disable(event);
+ if (x86_pmu.intel_cap.pebs_trap)
+ intel_pmu_lbr_disable(event);
}

static void intel_pmu_pebs_enable_all(void)
@@ -395,6 +397,12 @@ static int intel_pmu_pebs_fixup_ip(struc
unsigned long old_to, to = cpuc->lbr_entries[0].to;
unsigned long ip = regs->ip;

+ /*
+ * We don't need to fixup if the PEBS assist is fault like
+ */
+ if (!x86_pmu.intel_cap.pebs_trap)
+ return 1;
+
if (!cpuc->lbr_stack.nr || !from || !to)
return 0;

@@ -599,34 +607,26 @@ static void intel_ds_init(void)
x86_pmu.bts = boot_cpu_has(X86_FEATURE_BTS);
x86_pmu.pebs = boot_cpu_has(X86_FEATURE_PEBS);
if (x86_pmu.pebs) {
- int format = 0;
-
- if (x86_pmu.version > 1) {
- u64 capabilities;
- /*
- * v2+ has a PEBS format field
- */
- rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
- format = (capabilities >> 8) & 0xf;
- }
+ char pebs_type = x86_pmu.intel_cap.pebs_trap ? '+' : '-';
+ int format = x86_pmu.intel_cap.pebs_format;

switch (format) {
case 0:
- printk(KERN_CONT "PEBS v0, ");
+ printk(KERN_CONT "PEBS fmt0%c, ", pebs_type);
x86_pmu.pebs_record_size = sizeof(struct pebs_record_core);
x86_pmu.drain_pebs = intel_pmu_drain_pebs_core;
x86_pmu.pebs_constraints = intel_core_pebs_events;
break;

case 1:
- printk(KERN_CONT "PEBS v1, ");
+ printk(KERN_CONT "PEBS fmt1%c, ", pebs_type);
x86_pmu.pebs_record_size = sizeof(struct pebs_record_nhm);
x86_pmu.drain_pebs = intel_pmu_drain_pebs_nhm;
x86_pmu.pebs_constraints = intel_nehalem_pebs_events;
break;

default:
- printk(KERN_CONT "PEBS unknown format: %d, ", format);
+ printk(KERN_CONT "no PEBS fmt%d%c, ", format, pebs_type);
x86_pmu.pebs = 0;
break;
}
Index: linux-2.6/arch/x86/kernel/cpu/perf_event_intel_lbr.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -53,7 +53,7 @@ static void intel_pmu_lbr_reset_64(void)

static void intel_pmu_lbr_reset(void)
{
- if (x86_pmu.lbr_format == LBR_FORMAT_32)
+ if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_32)
intel_pmu_lbr_reset_32();
else
intel_pmu_lbr_reset_64();
@@ -155,6 +155,7 @@ static void intel_pmu_lbr_read_32(struct
static void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
{
unsigned long mask = x86_pmu.lbr_nr - 1;
+ int lbr_format = x86_pmu.intel_cap.lbr_format;
u64 tos = intel_pmu_lbr_tos();
int i;

@@ -165,7 +166,7 @@ static void intel_pmu_lbr_read_64(struct
rdmsrl(x86_pmu.lbr_from + lbr_idx, from);
rdmsrl(x86_pmu.lbr_to + lbr_idx, to);

- if (x86_pmu.lbr_format == LBR_FORMAT_EIP_FLAGS) {
+ if (lbr_format == LBR_FORMAT_EIP_FLAGS) {
flags = !!(from & LBR_FROM_FLAG_MISPRED);
from = (u64)((((s64)from) << 1) >> 1);
}
@@ -184,23 +185,14 @@ static void intel_pmu_lbr_read(void)
if (!cpuc->lbr_users)
return;

- if (x86_pmu.lbr_format == LBR_FORMAT_32)
+ if (x86_pmu.intel_cap.lbr_format == LBR_FORMAT_32)
intel_pmu_lbr_read_32(cpuc);
else
intel_pmu_lbr_read_64(cpuc);
}

-static int intel_pmu_lbr_format(void)
-{
- u64 capabilities;
-
- rdmsrl(MSR_IA32_PERF_CAPABILITIES, capabilities);
- return capabilities & 0x1f;
-}
-
static void intel_pmu_lbr_init_core(void)
{
- x86_pmu.lbr_format = intel_pmu_lbr_format();
x86_pmu.lbr_nr = 4;
x86_pmu.lbr_tos = 0x01c9;
x86_pmu.lbr_from = 0x40;
@@ -209,7 +201,6 @@ static void intel_pmu_lbr_init_core(void

static void intel_pmu_lbr_init_nhm(void)
{
- x86_pmu.lbr_format = intel_pmu_lbr_format();
x86_pmu.lbr_nr = 16;
x86_pmu.lbr_tos = 0x01c9;
x86_pmu.lbr_from = 0x680;
@@ -218,7 +209,6 @@ static void intel_pmu_lbr_init_nhm(void)

static void intel_pmu_lbr_init_atom(void)
{
- x86_pmu.lbr_format = intel_pmu_lbr_format();
x86_pmu.lbr_nr = 8;
x86_pmu.lbr_tos = 0x01c9;
x86_pmu.lbr_from = 0x40;
--



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