linux-kernel - [PATCH V8 07/14] perf, x86: allocate space for storing LBR stack

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Date:	Thu,  6 Nov 2014 09:54:24 -0500
From:	Kan Liang <kan.liang@...el.com>
To:	a.p.zijlstra@...llo.nl, eranian@...gle.com
Cc:	linux-kernel@...r.kernel.org, mingo@...hat.com, paulus@...ba.org,
	acme@...nel.org, jolsa@...hat.com, ak@...ux.intel.com,
	Kan Liang <kan.liang@...el.com>
Subject: [PATCH V8 07/14] perf, x86: allocate space for storing LBR stack

From: Yan, Zheng <zheng.z.yan@...el.com>

When the LBR call stack is enabled, it is necessary to save/restore
the LBR stack on context switch. We can use pmu specific data to
store LBR stack when task is scheduled out. This patch adds code
that allocates the pmu specific data.

Signed-off-by: Yan, Zheng <zheng.z.yan@...el.com>
Signed-off-by: Kan Liang <kan.liang@...el.com>
Reviewed-by: Stephane Eranian <eranian@...gle.com>
---
 arch/x86/kernel/cpu/perf_event.c | 4 ++++
 arch/x86/kernel/cpu/perf_event.h | 7 +++++++
 2 files changed, 11 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index e37adf0..1fd9492 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -428,6 +428,9 @@ int x86_pmu_hw_config(struct perf_event *event)
 		}
 	}
 
+	if (event->attr.branch_sample_type & PERF_SAMPLE_BRANCH_CALL_STACK)
+		event->attach_state |= PERF_ATTACH_TASK_DATA;
+
 	/*
 	 * Generate PMC IRQs:
 	 * (keep 'enabled' bit clear for now)
@@ -1912,6 +1915,7 @@ static struct pmu pmu = {
 
 	.event_idx		= x86_pmu_event_idx,
 	.sched_task		= x86_pmu_sched_task,
+	.task_ctx_size          = sizeof(struct x86_perf_task_context),
 };
 
 void arch_perf_update_userpage(struct perf_event_mmap_page *userpg, u64 now)
diff --git a/arch/x86/kernel/cpu/perf_event.h b/arch/x86/kernel/cpu/perf_event.h
index 13464e4..b4568e5 100644
--- a/arch/x86/kernel/cpu/perf_event.h
+++ b/arch/x86/kernel/cpu/perf_event.h
@@ -510,6 +510,13 @@ struct x86_pmu {
 	struct perf_guest_switch_msr *(*guest_get_msrs)(int *nr);
 };
 
+struct x86_perf_task_context {
+	u64 lbr_from[MAX_LBR_ENTRIES];
+	u64 lbr_to[MAX_LBR_ENTRIES];
+	int lbr_callstack_users;
+	int lbr_stack_state;
+};
+
 enum {
 	PERF_SAMPLE_BRANCH_CALL_STACK_SHIFT = PERF_SAMPLE_BRANCH_MAX_SHIFT,
 	PERF_SAMPLE_BRANCH_SELECT_MAP_SIZE,
-- 
1.8.3.2

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