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From:   Luwei Kang <luwei.kang@intel.com>
To:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org
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        kan.liang@linux.intel.com, like.xu@linux.intel.com
Subject: [PATCH v1 03/11] perf/x86: Expose a function to disable auto-reload
Date:   Fri,  6 Mar 2020 01:56:57 +0800
Message-Id: <1583431025-19802-4-git-send-email-luwei.kang@intel.com>
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References: <1583431025-19802-1-git-send-email-luwei.kang@intel.com>
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From: Kan Liang <kan.liang@linux.intel.com>

KVM needs to disable PEBS auto-reload for guest owned event to avoid
unnecessory drain_pebs() in host.

Expose a function to disable auto-reload mechanism by unset the related
flag. The function has to be invoked before event enabling, otherwise
there is no effect.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 arch/x86/events/intel/core.c      | 14 ++++++++++++++
 arch/x86/include/asm/perf_event.h |  2 ++
 2 files changed, 16 insertions(+)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index ef95076..cd17601 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3299,6 +3299,20 @@ static int core_pmu_hw_config(struct perf_event *event)
 	return intel_pmu_bts_config(event);
 }
 
+/*
+ * Disable PEBS auto-reload mechanism by unset the flag.
+ * The function has to be invoked before event enabling,
+ * otherwise there is no effect.
+ *
+ * Currently, it's used by KVM to disable PEBS auto-reload
+ * for guest owned event.
+ */
+void perf_x86_pmu_unset_auto_reload(struct perf_event *event)
+{
+	event->hw.flags &= ~PERF_X86_EVENT_AUTO_RELOAD;
+}
+EXPORT_SYMBOL_GPL(perf_x86_pmu_unset_auto_reload);
+
 static int intel_pmu_hw_config(struct perf_event *event)
 {
 	int ret = x86_pmu_hw_config(event);
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 29964b0..6179234 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -325,6 +325,7 @@ struct perf_guest_switch_msr {
 extern void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap);
 extern void perf_check_microcode(void);
 extern int x86_perf_rdpmc_index(struct perf_event *event);
+extern void perf_x86_pmu_unset_auto_reload(struct perf_event *event);
 #else
 static inline void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
 {
@@ -333,6 +334,7 @@ static inline void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
 
 static inline void perf_events_lapic_init(void)	{ }
 static inline void perf_check_microcode(void) { }
+static inline void perf_x86_pmu_unset_auto_reload(struct perf_event *event) { }
 #endif
 
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
-- 
1.8.3.1