[Patch v5 05/18] perf/x86: Add lbr_enabled to track LBR state

[Dapeng Mi]

Add a lbr_enabled flag to track whether LBR is enabled. This will be
used by a subsequent change to avoid blindly re-enabling LBR in
perf_snapshot_branch_stack() without checking whether LBR has already
been disabled.

Fixes: c22ac2a3d4bd ("perf: Enable branch record for software events")
Fixes: a4d18112e531 ("perf/x86/amd: Support capturing LBR from software events")
Signed-off-by: Dapeng Mi <dapeng1.mi@xxxxxxxxxxxxxxx>
---
 arch/x86/events/amd/lbr.c    | 2 ++
 arch/x86/events/intel/core.c | 5 +++++
 arch/x86/events/intel/lbr.c  | 2 ++
 arch/x86/events/perf_event.h | 9 +++++++++
 4 files changed, 18 insertions(+)

diff --git a/arch/x86/events/amd/lbr.c b/arch/x86/events/amd/lbr.c
index 46bd3ce1d614..cf11e4815c39 100644
--- a/arch/x86/events/amd/lbr.c
+++ b/arch/x86/events/amd/lbr.c
@@ -399,6 +399,8 @@ void amd_pmu_lbr_enable_all(void)
 	if (!cpuc->lbr_users || !x86_pmu.lbr_nr)
 		return;
 
+	cpuc->lbr_enabled = 1;
+
 	/* Set hardware branch filter */
 	if (cpuc->lbr_select) {
 		lbr_select = cpuc->lbr_sel->config & LBR_SELECT_MASK;
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 18cae4ac32b6..0ed0269189ba 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -4001,6 +4001,11 @@ static int intel_pmu_handle_irq(struct pt_regs *regs)
 	 * It needs to be restored when leaving the handler.
 	 */
 	pmu_enabled = cpuc->enabled;
+
+	/* If pmu version < 4, LBR freeze disables LBR. */
+	if (x86_pmu.version < 4)
+		cpuc->lbr_enabled = 0;
+
 	/*
 	 * In general, the early ACK is only applied for old platforms.
 	 * For the big core starts from Haswell, the late ACK should be
diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 1ae853f7ac1a..ee724b28d90c 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -132,6 +132,8 @@ static void __intel_pmu_lbr_enable(bool pmi)
 	if (pmi && x86_pmu.version >= 4)
 		return;
 
+	cpuc->lbr_enabled = 1;
+
 	/*
 	 * No need to reprogram LBR_SELECT in a PMI, as it
 	 * did not change.
diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index e274802ef062..a4aab8130e92 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -473,6 +473,7 @@ struct cpu_hw_events {
 	unsigned long		active_mask[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
 	unsigned long		dirty[BITS_TO_LONGS(X86_PMC_IDX_MAX)];
 	int			enabled;
+	int			lbr_enabled;
 
 	int			n_events; /* the # of events in the below arrays */
 	int			n_added;  /* the # last events in the below arrays;
@@ -1676,8 +1677,11 @@ int amd_pmu_lbr_hw_config(struct perf_event *event);
 
 static __always_inline void __amd_pmu_lbr_disable(void)
 {
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	u64 dbg_ctl, dbg_extn_cfg;
 
+	cpuc->lbr_enabled = 0;
+
 	rdmsrq(MSR_AMD_DBG_EXTN_CFG, dbg_extn_cfg);
 	wrmsrq(MSR_AMD_DBG_EXTN_CFG, dbg_extn_cfg & ~DBG_EXTN_CFG_LBRV2EN);
 
@@ -1829,13 +1833,18 @@ static __always_inline void __intel_pmu_pebs_disable_all(void)
 
 static __always_inline void __intel_pmu_arch_lbr_disable(void)
 {
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+
+	cpuc->lbr_enabled = 0;
 	wrmsrq(MSR_ARCH_LBR_CTL, 0);
 }
 
 static __always_inline void __intel_pmu_lbr_disable(void)
 {
+	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	u64 debugctl;
 
+	cpuc->lbr_enabled = 0;
 	rdmsrq(MSR_IA32_DEBUGCTLMSR, debugctl);
 	debugctl &= ~(DEBUGCTLMSR_LBR | DEBUGCTLMSR_FREEZE_LBRS_ON_PMI);
 	wrmsrq(MSR_IA32_DEBUGCTLMSR, debugctl);
-- 
2.34.1