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Subject[PATCH V2 19/23] perf/x86/intel: Support CPUID 10.ECX to disable fixed counters
Date
From: Andi Kleen <ak@linux.intel.com>

Icelake supports a new CPUID 10.ECX cpu leaf to indicate some fixed
counters are not supported. This extends the previous count to a bitmap
which allows to disable even lower counters.

It's a nop on Icelake (all fixed counters are supported), but let's
implement it here. This adds the necessary checks. In theory it could
be used today by a Hypervisor.

For disabled counters disable any constraint events. I reuse the
existing intel_ctrl variable to remember which counters are disabled.
All code that reads all counters is fixed to check this extra bitmask.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---

No changes since V1.

arch/x86/events/core.c | 8 +++++++-
arch/x86/events/intel/core.c | 22 +++++++++++++++-------
arch/x86/events/perf_event.h | 6 ++++++
3 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index b9bee53e53d8..12d7d591843e 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -225,6 +225,8 @@ static bool check_hw_exists(void)
if (ret)
goto msr_fail;
for (i = 0; i < x86_pmu.num_counters_fixed; i++) {
+ if (fixed_counter_disabled(i))
+ continue;
if (val & (0x03 << i*4)) {
bios_fail = 1;
val_fail = val;
@@ -1372,6 +1374,8 @@ void perf_event_print_debug(void)
cpu, idx, prev_left);
}
for (idx = 0; idx < x86_pmu.num_counters_fixed; idx++) {
+ if (fixed_counter_disabled(idx))
+ continue;
rdmsrl(MSR_ARCH_PERFMON_FIXED_CTR0 + idx, pmc_count);

pr_info("CPU#%d: fixed-PMC%d count: %016llx\n",
@@ -1887,7 +1891,9 @@ static int __init init_hw_perf_events(void)
pr_info("... generic registers: %d\n", x86_pmu.num_counters);
pr_info("... value mask: %016Lx\n", x86_pmu.cntval_mask);
pr_info("... max period: %016Lx\n", x86_pmu.max_period);
- pr_info("... fixed-purpose events: %d\n", x86_pmu.num_counters_fixed);
+ pr_info("... fixed-purpose events: %lu\n",
+ hweight64((((1ULL << x86_pmu.num_counters_fixed) - 1)
+ << INTEL_PMC_IDX_FIXED) & x86_pmu.intel_ctrl));
pr_info("... event mask: %016Lx\n", x86_pmu.intel_ctrl);

/*
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index ef6045544628..a4b7711ef0ee 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2311,8 +2311,11 @@ static void intel_pmu_reset(void)
wrmsrl_safe(x86_pmu_config_addr(idx), 0ull);
wrmsrl_safe(x86_pmu_event_addr(idx), 0ull);
}
- for (idx = 0; idx < x86_pmu.num_counters_fixed; idx++)
+ for (idx = 0; idx < x86_pmu.num_counters_fixed; idx++) {
+ if (fixed_counter_disabled(idx))
+ continue;
wrmsrl_safe(MSR_ARCH_PERFMON_FIXED_CTR0 + idx, 0ull);
+ }

if (ds)
ds->bts_index = ds->bts_buffer_base;
@@ -4551,7 +4554,7 @@ __init int intel_pmu_init(void)
union cpuid10_eax eax;
union cpuid10_ebx ebx;
struct event_constraint *c;
- unsigned int unused;
+ unsigned int fixed_mask;
struct extra_reg *er;
int version, i;
char *name;
@@ -4572,9 +4575,11 @@ __init int intel_pmu_init(void)
* Check whether the Architectural PerfMon supports
* Branch Misses Retired hw_event or not.
*/
- cpuid(10, &eax.full, &ebx.full, &unused, &edx.full);
+ cpuid(10, &eax.full, &ebx.full, &fixed_mask, &edx.full);
if (eax.split.mask_length < ARCH_PERFMON_EVENTS_COUNT)
return -ENODEV;
+ if (!fixed_mask)
+ fixed_mask = -1;

version = eax.split.version_id;
if (version < 2)
@@ -5104,7 +5109,8 @@ __init int intel_pmu_init(void)
}

x86_pmu.intel_ctrl |=
- ((1LL << x86_pmu.num_counters_fixed)-1) << INTEL_PMC_IDX_FIXED;
+ (((1LL << x86_pmu.num_counters_fixed)-1) & (u64)fixed_mask)
+ << INTEL_PMC_IDX_FIXED;

if (x86_pmu.event_constraints) {
/*
@@ -5121,9 +5127,11 @@ __init int intel_pmu_init(void)
c->weight = hweight64(c->idxmsk64);
continue;
}
- if (c->cmask == FIXED_EVENT_FLAGS
- && c->idxmsk64 != INTEL_PMC_MSK_FIXED_REF_CYCLES) {
- c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
+ if (c->cmask == FIXED_EVENT_FLAGS) {
+ if (c->idxmsk64 != INTEL_PMC_MSK_FIXED_REF_CYCLES)
+ c->idxmsk64 |= (1ULL << x86_pmu.num_counters) - 1;
+ /* Disabled fixed counters which are not in CPUID */
+ c->idxmsk64 &= x86_pmu.intel_ctrl;
}
c->idxmsk64 &=
~(~0ULL << (INTEL_PMC_IDX_FIXED + x86_pmu.num_counters_fixed));
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index bd0dbbc2adeb..c1e1b5407449 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -926,6 +926,12 @@ ssize_t events_sysfs_show(struct device *dev, struct device_attribute *attr,
ssize_t events_ht_sysfs_show(struct device *dev, struct device_attribute *attr,
char *page);

+static inline bool fixed_counter_disabled(int i)
+{
+ return x86_pmu.intel_ctrl &&
+ ((1ULL << (i + INTEL_PMC_IDX_FIXED)) & x86_pmu.intel_ctrl);
+}
+
#ifdef CONFIG_CPU_SUP_AMD

int amd_pmu_init(void);
--
2.17.1
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