linux-kernel - [RFC][PATCH 1/9] x86/perf/amd: Remove tracing from perf_lopwr

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Date:   Thu, 19 May 2022 23:27:51 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     frederic@...nel.org, paulmck@...nel.org, rjw@...ysocki.net,
        x86@...nel.org, eranian@...gle.com
Cc:     linux-kernel@...r.kernel.org, peterz@...radead.org,
        jpoimboe@...nel.org
Subject: [RFC][PATCH 1/9] x86/perf/amd: Remove tracing from perf_lopwr_cb()

The perf_lopwr_cb() is called from the idle routines; there is no RCU
there, we must not enter tracing.

Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 arch/x86/events/amd/brs.c |   13 +++++--------
 1 file changed, 5 insertions(+), 8 deletions(-)

--- a/arch/x86/events/amd/brs.c
+++ b/arch/x86/events/amd/brs.c
@@ -41,18 +41,15 @@ static inline unsigned int brs_to(int id
 	return MSR_AMD_SAMP_BR_FROM + 2 * idx + 1;
 }
 
-static inline void set_debug_extn_cfg(u64 val)
+static __always_inline void set_debug_extn_cfg(u64 val)
 {
 	/* bits[4:3] must always be set to 11b */
-	wrmsrl(MSR_AMD_DBG_EXTN_CFG, val | 3ULL << 3);
+	__wrmsr(MSR_AMD_DBG_EXTN_CFG, val | 3ULL << 3, val >> 32);
 }
 
-static inline u64 get_debug_extn_cfg(void)
+static __always_inline u64 get_debug_extn_cfg(void)
 {
-	u64 val;
-
-	rdmsrl(MSR_AMD_DBG_EXTN_CFG, val);
-	return val;
+	return __rdmsr(MSR_AMD_DBG_EXTN_CFG);
 }
 
 static bool __init amd_brs_detect(void)
@@ -338,7 +335,7 @@ void amd_pmu_brs_sched_task(struct perf_
  * called from ACPI processor_idle.c or acpi_pad.c
  * with interrupts disabled
  */
-void perf_amd_brs_lopwr_cb(bool lopwr_in)
+void noinstr perf_amd_brs_lopwr_cb(bool lopwr_in)
 {
 	struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
 	union amd_debug_extn_cfg cfg;