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Subject[V3][PATCH 5/7] perf, x86: Implement IBS pmu control ops
Date
Add code to control the IBS pmu. We need to maintain per-cpu
states. Since some states are used and changed by the nmi handler,
access to these states must be atomic.

Signed-off-by: Robert Richter <robert.richter@amd.com>
---
arch/x86/kernel/cpu/perf_event_amd_ibs.c | 106 +++++++++++++++++++++++++++++-
1 files changed, 103 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_amd_ibs.c b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
index 57b38d5..9713d31 100644
--- a/arch/x86/kernel/cpu/perf_event_amd_ibs.c
+++ b/arch/x86/kernel/cpu/perf_event_amd_ibs.c
@@ -22,6 +22,19 @@ static u32 ibs_caps;
#define IBS_FETCH_CONFIG_MASK (IBS_FETCH_RAND_EN | IBS_FETCH_MAX_CNT)
#define IBS_OP_CONFIG_MASK IBS_OP_MAX_CNT

+enum ibs_states {
+ IBS_ENABLED = 0,
+ IBS_STARTED = 1,
+ IBS_STOPPING = 2,
+
+ IBS_MAX_STATES,
+};
+
+struct cpu_perf_ibs {
+ struct perf_event *event;
+ unsigned long state[BITS_TO_LONGS(IBS_MAX_STATES)];
+};
+
struct perf_ibs {
struct pmu pmu;
unsigned int msr;
@@ -31,6 +44,7 @@ struct perf_ibs {
u64 valid_mask;
unsigned long offset_mask[1];
int offset_max;
+ struct cpu_perf_ibs __percpu *pcpu;
};

struct perf_ibs_data {
@@ -95,15 +109,66 @@ static int perf_ibs_init(struct perf_event *event)
return 0;
}

+static void perf_ibs_start(struct perf_event *event, int flags)
+{
+ struct hw_perf_event *hwc = &event->hw;
+ struct perf_ibs *perf_ibs = container_of(event->pmu, struct perf_ibs, pmu);
+ struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu);
+
+ if (test_and_set_bit(IBS_STARTED, pcpu->state))
+ return;
+
+ wrmsrl(hwc->config_base, hwc->config | perf_ibs->enable_mask);
+}
+
+static void perf_ibs_stop(struct perf_event *event, int flags)
+{
+ struct hw_perf_event *hwc = &event->hw;
+ struct perf_ibs *perf_ibs = container_of(event->pmu, struct perf_ibs, pmu);
+ struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu);
+ u64 val;
+
+ if (!test_and_clear_bit(IBS_STARTED, pcpu->state))
+ return;
+
+ set_bit(IBS_STOPPING, pcpu->state);
+
+ rdmsrl(hwc->config_base, val);
+ val &= ~perf_ibs->enable_mask;
+ wrmsrl(hwc->config_base, val);
+}
+
static int perf_ibs_add(struct perf_event *event, int flags)
{
+ struct perf_ibs *perf_ibs = container_of(event->pmu, struct perf_ibs, pmu);
+ struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu);
+
+ if (test_and_set_bit(IBS_ENABLED, pcpu->state))
+ return -ENOSPC;
+
+ pcpu->event = event;
+
+ if (flags & PERF_EF_START)
+ perf_ibs_start(event, PERF_EF_RELOAD);
+
return 0;
}

static void perf_ibs_del(struct perf_event *event, int flags)
{
+ struct perf_ibs *perf_ibs = container_of(event->pmu, struct perf_ibs, pmu);
+ struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu);
+
+ if (!test_and_clear_bit(IBS_ENABLED, pcpu->state))
+ return;
+
+ perf_ibs_stop(event, 0);
+
+ pcpu->event = NULL;
}

+static void perf_ibs_read(struct perf_event *event) { }
+
static struct perf_ibs perf_ibs_fetch = {
.pmu = {
.task_ctx_nr = perf_invalid_context,
@@ -111,6 +176,9 @@ static struct perf_ibs perf_ibs_fetch = {
.event_init = perf_ibs_init,
.add = perf_ibs_add,
.del = perf_ibs_del,
+ .start = perf_ibs_start,
+ .stop = perf_ibs_stop,
+ .read = perf_ibs_read,
},
.msr = MSR_AMD64_IBSFETCHCTL,
.config_mask = IBS_FETCH_CONFIG_MASK,
@@ -128,6 +196,9 @@ static struct perf_ibs perf_ibs_op = {
.event_init = perf_ibs_init,
.add = perf_ibs_add,
.del = perf_ibs_del,
+ .start = perf_ibs_start,
+ .stop = perf_ibs_stop,
+ .read = perf_ibs_read,
},
.msr = MSR_AMD64_IBSOPCTL,
.config_mask = IBS_OP_CONFIG_MASK,
@@ -140,7 +211,8 @@ static struct perf_ibs perf_ibs_op = {

static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
{
- struct perf_event *event = NULL;
+ struct cpu_perf_ibs *pcpu = this_cpu_ptr(perf_ibs->pcpu);
+ struct perf_event *event = pcpu->event;
struct hw_perf_event *hwc = &event->hw;
struct perf_sample_data data;
struct perf_raw_record raw;
@@ -150,6 +222,14 @@ static int perf_ibs_handle_irq(struct perf_ibs *perf_ibs, struct pt_regs *iregs)
unsigned int msr;
u64 *buf;

+ if (!test_bit(IBS_STARTED, pcpu->state)) {
+ /* Catch spurious interrupts after stopping IBS: */
+ if (!test_and_clear_bit(IBS_STOPPING, pcpu->state))
+ return 0;
+ rdmsrl(perf_ibs->msr, *ibs_data.regs);
+ return (*ibs_data.regs & perf_ibs->valid_mask);
+ }
+
msr = hwc->config_base;
buf = ibs_data.regs;
rdmsrl(msr, *buf);
@@ -198,13 +278,33 @@ perf_ibs_nmi_handler(unsigned int cmd, struct pt_regs *regs)
return handled;
}

+static __init int perf_ibs_pmu_init(struct perf_ibs *perf_ibs, char *name)
+{
+ struct cpu_perf_ibs __percpu *pcpu;
+ int ret;
+
+ pcpu = alloc_percpu(struct cpu_perf_ibs);
+ if (!pcpu)
+ return -ENOMEM;
+
+ perf_ibs->pcpu = pcpu;
+
+ ret = perf_pmu_register(&perf_ibs->pmu, name, -1);
+ if (ret) {
+ perf_ibs->pcpu = NULL;
+ free_percpu(pcpu);
+ }
+
+ return ret;
+}
+
static __init int perf_event_ibs_init(void)
{
if (!ibs_caps)
return -ENODEV; /* ibs not supported by the cpu */

- perf_pmu_register(&perf_ibs_fetch.pmu, "ibs_fetch", -1);
- perf_pmu_register(&perf_ibs_op.pmu, "ibs_op", -1);
+ perf_ibs_pmu_init(&perf_ibs_fetch, "ibs_fetch");
+ perf_ibs_pmu_init(&perf_ibs_op, "ibs_op");
register_nmi_handler(NMI_LOCAL, &perf_ibs_nmi_handler, 0, "perf_ibs");
printk(KERN_INFO "perf: AMD IBS detected (0x%08x)\n", ibs_caps);

--
1.7.6.1



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