linux-kernel - [PATCH] x86/perf: Fixed obtaining address error about performance monitor MSR on old Inel CPU.

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Date:   Mon, 7 Jun 2021 10:53:35 +0800
From:   Cody Yao-oc <CodyYao-oc@...oxin.com>
To:     <peterz@...radead.org>, <mingo@...hat.com>, <acme@...nel.org>,
        <mark.rutland@....com>, <alexander.shishkin@...ux.intel.com>,
        <jolsa@...hat.com>, <namhyung@...nel.org>, <tglx@...utronix.de>,
        <bp@...en8.de>, <hpa@...or.com>, <x86@...nel.org>
CC:     <linux-perf-users@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <shyaololo@....com>, CodyYao-oc <CodyYao-oc@...oxin.com>
Subject: [PATCH] x86/perf: Fixed obtaining address error about performance monitor MSR on old Inel CPU.

From: CodyYao-oc <CodyYao-oc@...oxin.com>

Fix "obtain wrong msr address" bug in function nmi_perfctr_msr_to_bit
and nmi_eventsel_msr_to_bit. In X86_VENDOR_INTEL switch branch, if all
of the check conditions are not met, code flow will slip to
X86_VENDOR_ZHAOXIN branch which may lead to incorrect information.

Using fallthrough instead of break was completely unintentional,
therefore, "fallthrough" should be changed to "break".

Fixes: 3a4ac121c2ca ("x86/perf: Add hardware performance events support for Zhaoxin CPU.")

Signed-off-by: CodyYao-oc <CodyYao-oc@...oxin.com>
---
 arch/x86/kernel/cpu/perfctr-watchdog.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perfctr-watchdog.c b/arch/x86/kernel/cpu/perfctr-watchdog.c
index 3ef5868ac588..7aecb2fc3186 100644
--- a/arch/x86/kernel/cpu/perfctr-watchdog.c
+++ b/arch/x86/kernel/cpu/perfctr-watchdog.c
@@ -63,7 +63,7 @@ static inline unsigned int nmi_perfctr_msr_to_bit(unsigned int msr)
 		case 15:
 			return msr - MSR_P4_BPU_PERFCTR0;
 		}
-		fallthrough;
+		break;
 	case X86_VENDOR_ZHAOXIN:
 	case X86_VENDOR_CENTAUR:
 		return msr - MSR_ARCH_PERFMON_PERFCTR0;
@@ -96,7 +96,7 @@ static inline unsigned int nmi_evntsel_msr_to_bit(unsigned int msr)
 		case 15:
 			return msr - MSR_P4_BSU_ESCR0;
 		}
-		fallthrough;
+		break;
 	case X86_VENDOR_ZHAOXIN:
 	case X86_VENDOR_CENTAUR:
 		return msr - MSR_ARCH_PERFMON_EVENTSEL0;
-- 
2.17.1