linux-kernel - [PATCH v3 1/3] perf/x86/core: Remove unnecessary stubs provided for KVM-only helpers

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Message-ID: <20220831000051.4015031-2-seanjc@google.com>
Date:   Wed, 31 Aug 2022 00:00:49 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, Like Xu <like.xu.linux@...il.com>
Subject: [PATCH v3 1/3] perf/x86/core: Remove unnecessary stubs provided for
 KVM-only helpers

Remove CONFIG_PERF_EVENT=n stubs for functions that are effectively
KVM-only.  KVM selects PERF_EVENT and will never consume the stubs.
Dropping the unnecessary stubs will allow simplifying x86_perf_get_lbr()
by getting rid of the impossible-to-hit error path (which KVM doesn't
even check).

Opportunstically reorganize the declarations to collapse multiple
CONFIG_PERF_EVENTS #ifdefs.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/perf_event.h | 53 ++++++++-----------------------
 1 file changed, 13 insertions(+), 40 deletions(-)

diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index f6fc8dd51ef4..f839eb55f298 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -525,46 +525,18 @@ extern u64 perf_get_hw_event_config(int hw_event);
 extern void perf_check_microcode(void);
 extern void perf_clear_dirty_counters(void);
 extern int x86_perf_rdpmc_index(struct perf_event *event);
-#else
-static inline void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
-{
-	memset(cap, 0, sizeof(*cap));
-}
 
-static inline u64 perf_get_hw_event_config(int hw_event)
-{
-	return 0;
-}
-
-static inline void perf_events_lapic_init(void)	{ }
-static inline void perf_check_microcode(void) { }
-#endif
-
-#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
+#ifdef CONFIG_CPU_SUP_INTEL
 extern struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr, void *data);
 extern int x86_perf_get_lbr(struct x86_pmu_lbr *lbr);
-#else
-struct perf_guest_switch_msr *perf_guest_get_msrs(int *nr, void *data);
-static inline int x86_perf_get_lbr(struct x86_pmu_lbr *lbr)
-{
-	return -1;
-}
-#endif
+extern void intel_pt_handle_vmx(int on);
+#endif /* CONFIG_CPU_SUP_INTEL */
 
-#ifdef CONFIG_CPU_SUP_INTEL
- extern void intel_pt_handle_vmx(int on);
-#else
-static inline void intel_pt_handle_vmx(int on)
-{
+#ifdef CONFIG_CPU_SUP_AMD
+extern void amd_pmu_enable_virt(void);
+extern void amd_pmu_disable_virt(void);
 
-}
-#endif
-
-#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_AMD)
- extern void amd_pmu_enable_virt(void);
- extern void amd_pmu_disable_virt(void);
-
-#if defined(CONFIG_PERF_EVENTS_AMD_BRS)
+#ifdef CONFIG_PERF_EVENTS_AMD_BRS
 
 #define PERF_NEEDS_LOPWR_CB 1
 
@@ -582,12 +554,13 @@ static inline void perf_lopwr_cb(bool lopwr_in)
 	static_call_mod(perf_lopwr_cb)(lopwr_in);
 }
 
-#endif /* PERF_NEEDS_LOPWR_CB */
+#endif /* CONFIG_PERF_EVENTS_AMD_BRS */
+#endif /* CONFIG_CPU_SUP_AMD */
 
-#else
- static inline void amd_pmu_enable_virt(void) { }
- static inline void amd_pmu_disable_virt(void) { }
-#endif
+#else  /* !CONFIG_PERF_EVENTS */
+static inline void perf_events_lapic_init(void)	{ }
+static inline void perf_check_microcode(void) { }
+#endif /* CONFIG_PERF_EVENTS */
 
 #define arch_perf_out_copy_user copy_from_user_nmi
 
-- 
2.37.2.672.g94769d06f0-goog