linux-kernel - [PATCH] x86/perf: Use static_call for x86_pmu.guest_get

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Date:   Mon, 18 Jan 2021 15:21:51 +0800
From:   Like Xu <like.xu@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Jason Baron <jbaron@...mai.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH] x86/perf: Use static_call for x86_pmu.guest_get_msrs

Clean up that CONFIG_RETPOLINE crud and replace the
indirect call x86_pmu.guest_get_msrs with static_call().

Suggested-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Signed-off-by: Like Xu <like.xu@...ux.intel.com>
---
 arch/x86/events/core.c       | 16 ++++++++++++++++
 arch/x86/events/intel/core.c | 20 --------------------
 2 files changed, 16 insertions(+), 20 deletions(-)

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index e37de298a495..2eec3c8d0a13 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -81,6 +81,8 @@ DEFINE_STATIC_CALL_NULL(x86_pmu_swap_task_ctx, *x86_pmu.swap_task_ctx);
 DEFINE_STATIC_CALL_NULL(x86_pmu_drain_pebs,   *x86_pmu.drain_pebs);
 DEFINE_STATIC_CALL_NULL(x86_pmu_pebs_aliases, *x86_pmu.pebs_aliases);
 
+DEFINE_STATIC_CALL_NULL(x86_pmu_guest_get_msrs,  *x86_pmu.guest_get_msrs);
+
 u64 __read_mostly hw_cache_event_ids
 				[PERF_COUNT_HW_CACHE_MAX]
 				[PERF_COUNT_HW_CACHE_OP_MAX]
@@ -665,6 +667,18 @@ void x86_pmu_disable_all(void)
 	}
 }
 
+struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
+{
+	struct perf_guest_switch_msr *ret = NULL;
+
+	ret = static_call(x86_pmu_guest_get_msrs)(nr);
+	if (!ret)
+		*nr = 0;
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(perf_guest_get_msrs);
+
 /*
  * There may be PMI landing after enabled=0. The PMI hitting could be before or
  * after disable_all.
@@ -1923,6 +1937,8 @@ static void x86_pmu_static_call_update(void)
 
 	static_call_update(x86_pmu_drain_pebs, x86_pmu.drain_pebs);
 	static_call_update(x86_pmu_pebs_aliases, x86_pmu.pebs_aliases);
+
+	static_call_update(x86_pmu_guest_get_msrs, x86_pmu.guest_get_msrs);
 }
 
 static void _x86_pmu_read(struct perf_event *event)
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index d4569bfa83e3..93adf53cce5f 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -3680,26 +3680,6 @@ static int intel_pmu_hw_config(struct perf_event *event)
 	return 0;
 }
 
-#ifdef CONFIG_RETPOLINE
-static struct perf_guest_switch_msr *core_guest_get_msrs(int *nr);
-static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr);
-#endif
-
-struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr)
-{
-#ifdef CONFIG_RETPOLINE
-	if (x86_pmu.guest_get_msrs == intel_guest_get_msrs)
-		return intel_guest_get_msrs(nr);
-	else if (x86_pmu.guest_get_msrs == core_guest_get_msrs)
-		return core_guest_get_msrs(nr);
-#endif
-	if (x86_pmu.guest_get_msrs)
-		return x86_pmu.guest_get_msrs(nr);
-	*nr = 0;
-	return NULL;
-}
-EXPORT_SYMBOL_GPL(perf_guest_get_msrs);
-
 static struct perf_guest_switch_msr *intel_guest_get_msrs(int *nr)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
-- 
2.29.2