Re: [PATCH V6 2/5] perf/x86/kvm: Avoid unnecessary work in guest filtering

[Peter Zijlstra <peterz@infradead.org>]

This then? That's nearly what you had; except a lot less noisy.

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -18,6 +18,7 @@
 #include <asm/hardirq.h>
 #include <asm/intel-family.h>
 #include <asm/apic.h>
+#include <asm/cpu_device_id.h>
 
 #include "../perf_event.h"
 
@@ -3206,16 +3207,27 @@ static struct perf_guest_switch_msr *int
 	arr[0].msr = MSR_CORE_PERF_GLOBAL_CTRL;
 	arr[0].host = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_guest_mask;
 	arr[0].guest = x86_pmu.intel_ctrl & ~cpuc->intel_ctrl_host_mask;
-	/*
-	 * If PMU counter has PEBS enabled it is not enough to disable counter
-	 * on a guest entry since PEBS memory write can overshoot guest entry
-	 * and corrupt guest memory. Disabling PEBS solves the problem.
-	 */
-	arr[1].msr = MSR_IA32_PEBS_ENABLE;
-	arr[1].host = cpuc->pebs_enabled;
-	arr[1].guest = 0;
+	if (x86_pmu.flags & PMU_FL_PEBS_ALL)
+		arr[0].guest &= ~cpuc->pebs_enabled;
+	else
+		arr[0].guest &= ~(cpuc->pebs_enabled & PEBS_COUNTER_MASK);
+	*nr = 1;
+
+	if (x86_pmu.pebs && x86_pmu.pebs_no_isolation) {
+		/*
+		 * If PMU counter has PEBS enabled it is not enough to
+		 * disable counter on a guest entry since PEBS memory
+		 * write can overshoot guest entry and corrupt guest
+		 * memory. Disabling PEBS solves the problem.
+		 *
+		 * Don't do this if the CPU already enforces it.
+		 */
+		arr[1].msr = MSR_IA32_PEBS_ENABLE;
+		arr[1].host = cpuc->pebs_enabled;
+		arr[1].guest = 0;
+		*nr = 2;
+	}
 
-	*nr = 2;
 	return arr;
 }
 
@@ -3739,6 +3751,48 @@ static __init void intel_clovertown_quir
 	x86_pmu.pebs_constraints = NULL;
 }
 
+static const struct x86_cpu_desc isolation_ucodes[] = {
+	INTEL_CPU_DESC(INTEL_FAM6_HASWELL_CORE,		 3, 0x0000001f),
+	INTEL_CPU_DESC(INTEL_FAM6_HASWELL_ULT,		 1, 0x0000001e),
+	INTEL_CPU_DESC(INTEL_FAM6_HASWELL_GT3E,		 1, 0x00000015),
+	INTEL_CPU_DESC(INTEL_FAM6_HASWELL_X,		 2, 0x00000037),
+	INTEL_CPU_DESC(INTEL_FAM6_HASWELL_X,		 4, 0x0000000a),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_CORE,	 4, 0x00000023),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_GT3E,	 1, 0x00000014),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D,	 2, 0x00000010),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D,	 3, 0x07000009),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D,	 4, 0x0f000009),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_XEON_D,	 5, 0x0e000002),
+	INTEL_CPU_DESC(INTEL_FAM6_BROADWELL_X,		 2, 0x0b000014),
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X,		 3, 0x00000021),
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_X,		 4, 0x00000000),
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_MOBILE,	 3, 0x0000007c),
+	INTEL_CPU_DESC(INTEL_FAM6_SKYLAKE_DESKTOP,	 3, 0x0000007c),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	 9, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	 9, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	10, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	11, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_MOBILE,	12, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	10, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	11, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	12, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_KABYLAKE_DESKTOP,	13, 0x0000004e),
+	INTEL_CPU_DESC(INTEL_FAM6_CANNONLAKE_MOBILE,	 3, 0x00000000),
+	{}
+};
+
+static void intel_check_pebs_isolation(void)
+{
+	x86_pmu.pebs_no_isolation = !x86_cpu_has_min_microcode_rev(isolation_ucodes);
+}
+
+static __init void intel_pebs_isolation_quirk(void)
+{
+	WARN_ON_ONCE(x86_pmu.check_microcode);
+	x86_pmu.check_microcode = intel_check_pebs_isolation;
+	intel_check_pebs_isolation();
+}
+
 static int intel_snb_pebs_broken(int cpu)
 {
 	u32 rev = UINT_MAX; /* default to broken for unknown models */
@@ -4433,6 +4487,7 @@ __init int intel_pmu_init(void)
 	case INTEL_FAM6_HASWELL_ULT:
 	case INTEL_FAM6_HASWELL_GT3E:
 		x86_add_quirk(intel_ht_bug);
+		x86_add_quirk(intel_pebs_isolation_quirk);
 		x86_pmu.late_ack = true;
 		memcpy(hw_cache_event_ids, hsw_hw_cache_event_ids, sizeof(hw_cache_event_ids));
 		memcpy(hw_cache_extra_regs, hsw_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
@@ -4464,6 +4519,7 @@ __init int intel_pmu_init(void)
 	case INTEL_FAM6_BROADWELL_XEON_D:
 	case INTEL_FAM6_BROADWELL_GT3E:
 	case INTEL_FAM6_BROADWELL_X:
+		x86_add_quirk(intel_pebs_isolation_quirk);
 		x86_pmu.late_ack = true;
 		memcpy(hw_cache_event_ids, hsw_hw_cache_event_ids, sizeof(hw_cache_event_ids));
 		memcpy(hw_cache_extra_regs, hsw_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
@@ -4526,6 +4582,7 @@ __init int intel_pmu_init(void)
 	case INTEL_FAM6_SKYLAKE_X:
 	case INTEL_FAM6_KABYLAKE_MOBILE:
 	case INTEL_FAM6_KABYLAKE_DESKTOP:
+		x86_add_quirk(intel_pebs_isolation_quirk);
 		x86_pmu.late_ack = true;
 		memcpy(hw_cache_event_ids, skl_hw_cache_event_ids, sizeof(hw_cache_event_ids));
 		memcpy(hw_cache_extra_regs, skl_hw_cache_extra_regs, sizeof(hw_cache_extra_regs));
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1628,6 +1628,7 @@ void __init intel_ds_init(void)
 	x86_pmu.bts  = boot_cpu_has(X86_FEATURE_BTS);
 	x86_pmu.pebs = boot_cpu_has(X86_FEATURE_PEBS);
 	x86_pmu.pebs_buffer_size = PEBS_BUFFER_SIZE;
+	x86_pmu.pebs_no_isolation = 1;
 	if (x86_pmu.pebs) {
 		char pebs_type = x86_pmu.intel_cap.pebs_trap ?  '+' : '-';
 		int format = x86_pmu.intel_cap.pebs_format;
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -601,13 +601,14 @@ struct x86_pmu {
 	/*
 	 * Intel DebugStore bits
 	 */
-	unsigned int	bts		:1,
-			bts_active	:1,
-			pebs		:1,
-			pebs_active	:1,
-			pebs_broken	:1,
-			pebs_prec_dist	:1,
-			pebs_no_tlb	:1;
+	unsigned int	bts			:1,
+			bts_active		:1,
+			pebs			:1,
+			pebs_active		:1,
+			pebs_broken		:1,
+			pebs_prec_dist		:1,
+			pebs_no_tlb		:1,
+			pebs_no_isolation	:1;
 	int		pebs_record_size;
 	int		pebs_buffer_size;
 	void		(*drain_pebs)(struct pt_regs *regs);