Re: [tip:perf/core] perf/x86: Add an MSR PMU driver

[Peter Zijlstra <peterz@infradead.org>]

On Thu, Aug 06, 2015 at 05:59:43PM +0200, Peter Zijlstra wrote:
> On Thu, Aug 06, 2015 at 08:30:08AM -0700, Andy Lutomirski wrote:
> > On Thu, Aug 6, 2015 at 8:21 AM, Peter Zijlstra <peterz@infradead.org> wrote:
> > > On Tue, Aug 04, 2015 at 08:39:27PM +0000, Liang, Kan wrote:
> > > -       default:
> > > -               err = -ENOTSUPP;
> > > +               if (!msr[i].test() || rdmsrl_safe(msr[i].msr, &val))
> > > +                       msr[i].attr = NULL;
> > 
> > IIRC rdmsrl_safe literally never fails under QEMU TCG, and I'm not
> 
> *sigh* the borkage never stops does it :-(
> 
> > entirely sure what happens under KVM if emulation kicks in.  It might
> > pay to keep the model check for the non-architectural stuff, or at
> > least check for a nonzero return value.
> 
> Of course, 0 might be a valid value.. Esp. for the SMI counter.

This then..

---
 arch/x86/kernel/cpu/perf_event_msr.c |  170 +++++++++++++++++------------------
 1 file changed, 85 insertions(+), 85 deletions(-)

--- a/arch/x86/kernel/cpu/perf_event_msr.c
+++ b/arch/x86/kernel/cpu/perf_event_msr.c
@@ -10,17 +10,63 @@ enum perf_msr_id {
 	PERF_MSR_EVENT_MAX,
 };
 
+bool test_aperfmperf(int idx)
+{
+	return boot_cpu_has(X86_FEATURE_APERFMPERF);
+}
+
+bool test_intel(int idx)
+{
+	if (boot_cpu_data.x86_vendor != X86_VENDOR_INTEL ||
+	    boot_cpu_data.x86 != 6)
+		return false;
+
+	switch (boot_cpu_data.x86_model) {
+	case 30: /* 45nm Nehalem    */
+	case 26: /* 45nm Nehalem-EP */
+	case 46: /* 45nm Nehalem-EX */
+
+	case 37: /* 32nm Westmere    */
+	case 44: /* 32nm Westmere-EP */
+	case 47: /* 32nm Westmere-EX */
+
+	case 42: /* 32nm SandyBridge         */
+	case 45: /* 32nm SandyBridge-E/EN/EP */
+
+	case 58: /* 22nm IvyBridge       */
+	case 62: /* 22nm IvyBridge-EP/EX */
+
+	case 60: /* 22nm Haswell Core */
+	case 63: /* 22nm Haswell Server */
+	case 69: /* 22nm Haswell ULT */
+	case 70: /* 22nm Haswell + GT3e (Intel Iris Pro graphics) */
+
+	case 61: /* 14nm Broadwell Core-M */
+	case 86: /* 14nm Broadwell Xeon D */
+	case 71: /* 14nm Broadwell + GT3e (Intel Iris Pro graphics) */
+	case 79: /* 14nm Broadwell Server */
+
+	case 55: /* 22nm Atom "Silvermont"                */
+	case 77: /* 22nm Atom "Silvermont Avoton/Rangely" */
+	case 76: /* 14nm Atom "Airmont"                   */
+		if (idx == PERF_MSR_SMI)
+			return true;
+		break;
+
+	case 78: /* 14nm Skylake Mobile */
+	case 94: /* 14nm Skylake Desktop */
+		if (idx == PERF_MSR_SMI || idx = PERF_MSR_PPERF)
+			return true;
+		break;
+	}
+
+	return false;
+}
+
 struct perf_msr {
-	int	id;
 	u64	msr;
-};
-
-static struct perf_msr msr[] = {
-	{ PERF_MSR_TSC, 0 },
-	{ PERF_MSR_APERF, MSR_IA32_APERF },
-	{ PERF_MSR_MPERF, MSR_IA32_MPERF },
-	{ PERF_MSR_PPERF, MSR_PPERF },
-	{ PERF_MSR_SMI, MSR_SMI_COUNT },
+	struct	perf_pmu_events_attr *attr;
+	bool	(*test)(int idx);
 };
 
 PMU_EVENT_ATTR_STRING(tsc,   evattr_tsc,   "event=0x00");
@@ -29,8 +75,16 @@ PMU_EVENT_ATTR_STRING(mperf, evattr_mper
 PMU_EVENT_ATTR_STRING(pperf, evattr_pperf, "event=0x03");
 PMU_EVENT_ATTR_STRING(smi,   evattr_smi,   "event=0x04");
 
+static struct perf_msr msr[] = {
+	[PERF_MSR_TSC]   = { 0,			&evattr_tsc,	NULL,		 },
+	[PERF_MSR_APERF] = { MSR_IA32_APERF,	&evattr_aperf,	test_aperfmperf, },
+	[PERF_MSR_MPERF] = { MSR_IA32_MPERF,	&evattr_mperf,	test_aperfmperf, },
+	[PERF_MSR_PPERF] = { MSR_PPERF,		&evattr_pperf,	test_intel,	 },
+	[PERF_MSR_SMI]   = { MSR_SMI_COUNT,	&evattr_smi,	test_intel,	 },
+};
+
 static struct attribute *events_attrs[PERF_MSR_EVENT_MAX + 1] = {
-	&evattr_tsc.attr.attr,
+	NULL,
 };
 
 static struct attribute_group events_attr_group = {
@@ -74,6 +128,9 @@ static int msr_event_init(struct perf_ev
 	    event->attr.sample_period) /* no sampling */
 		return -EINVAL;
 
+	if (!msr[cfg].attr)
+		return -EINVAL;
+
 	event->hw.idx = -1;
 	event->hw.event_base = msr[cfg].msr;
 	event->hw.config = cfg;
@@ -151,89 +208,32 @@ static struct pmu pmu_msr = {
 	.capabilities	= PERF_PMU_CAP_NO_INTERRUPT,
 };
 
-static int __init intel_msr_init(int idx)
-{
-	if (boot_cpu_data.x86 != 6)
-		return 0;
-
-	switch (boot_cpu_data.x86_model) {
-	case 30: /* 45nm Nehalem    */
-	case 26: /* 45nm Nehalem-EP */
-	case 46: /* 45nm Nehalem-EX */
-
-	case 37: /* 32nm Westmere    */
-	case 44: /* 32nm Westmere-EP */
-	case 47: /* 32nm Westmere-EX */
-
-	case 42: /* 32nm SandyBridge         */
-	case 45: /* 32nm SandyBridge-E/EN/EP */
-
-	case 58: /* 22nm IvyBridge       */
-	case 62: /* 22nm IvyBridge-EP/EX */
-
-	case 60: /* 22nm Haswell Core */
-	case 63: /* 22nm Haswell Server */
-	case 69: /* 22nm Haswell ULT */
-	case 70: /* 22nm Haswell + GT3e (Intel Iris Pro graphics) */
-
-	case 61: /* 14nm Broadwell Core-M */
-	case 86: /* 14nm Broadwell Xeon D */
-	case 71: /* 14nm Broadwell + GT3e (Intel Iris Pro graphics) */
-	case 79: /* 14nm Broadwell Server */
-		events_attrs[idx++] = &evattr_smi.attr.attr;
-		break;
-
-	case 78: /* 14nm Skylake Mobile */
-	case 94: /* 14nm Skylake Desktop */
-		events_attrs[idx++] = &evattr_pperf.attr.attr;
-		events_attrs[idx++] = &evattr_smi.attr.attr;
-		break;
-
-	case 55: /* 22nm Atom "Silvermont"                */
-	case 76: /* 14nm Atom "Airmont"                   */
-	case 77: /* 22nm Atom "Silvermont Avoton/Rangely" */
-		events_attrs[idx++] = &evattr_smi.attr.attr;
-		break;
-	}
-
-	events_attrs[idx] = NULL;
-
-	return 0;
-}
-
-static int __init amd_msr_init(int idx)
-{
-	return 0;
-}
-
 static int __init msr_init(void)
 {
-	int err;
-	int idx = 1;
+	int i, j = 0;
 
-	if (boot_cpu_has(X86_FEATURE_APERFMPERF)) {
-		events_attrs[idx++] = &evattr_aperf.attr.attr;
-		events_attrs[idx++] = &evattr_mperf.attr.attr;
-		events_attrs[idx] = NULL;
+	if (!boot_cpu_has(X86_FEATURE_TSC)) {
+		pr_cont("no MSR PMU driver.\n");
+		return 0;
 	}
 
-	switch (boot_cpu_data.x86_vendor) {
-	case X86_VENDOR_INTEL:
-		err = intel_msr_init(idx);
-		break;
-
-	case X86_VENDOR_AMD:
-		err = amd_msr_init(idx);
-		break;
-
-	default:
-		err = -ENOTSUPP;
+	/* Probe the MSRs. */
+	for (i = PERF_MSR_TSC + 1; i < PERF_MSR_EVENT_MAX; i++) {
+		u64 val;
+
+		/*
+		 * Virt sucks arse; you cannot tell if a R/O MSR is present :/
+		 */
+		if (!msr[i].test(i) || rdmsrl_safe(msr[i].msr, &val))
+			msr[i].attr = NULL;
 	}
 
-	if (err != 0) {
-		pr_cont("no msr PMU driver.\n");
-		return 0;
+	/* List remaining MSRs in the sysfs attrs. */
+	for (i = 0; i < PERF_MSR_EVENT_MAX; i++) {
+		if (msr[i].attr)
+			events_attrs[j++] = &msr[i].attr->attr.attr;
 	}
+	events_attrs[j] = NULL;
 
 	perf_pmu_register(&pmu_msr, "msr", -1);