linux-kernel - [PATCH 2/2] x86/tsc: Do feature check as the very first thing

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Date:   Sun, 18 Dec 2022 21:53:36 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH 2/2] x86/tsc: Do feature check as the very first thing

From: "Borislav Petkov (AMD)" <bp@...en8.de>

Do the feature check as the very first thing in the function. Everything
else comes after that and is meaningless work if the TSC CPUID bit is
not even set.

No functional changes.

Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 arch/x86/kernel/tsc.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c
index eaeffef93a12..1d509c8b3556 100644
--- a/arch/x86/kernel/tsc.c
+++ b/arch/x86/kernel/tsc.c
@@ -1509,6 +1509,11 @@ void __init tsc_early_init(void)
 
 void __init tsc_init(void)
 {
+	if (!boot_cpu_has(X86_FEATURE_TSC)) {
+		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
+		return;
+	}
+
 	/*
 	 * native_calibrate_cpu_early can only calibrate using methods that are
 	 * available early in boot.
@@ -1516,11 +1521,6 @@ void __init tsc_init(void)
 	if (x86_platform.calibrate_cpu == native_calibrate_cpu_early)
 		x86_platform.calibrate_cpu = native_calibrate_cpu;
 
-	if (!boot_cpu_has(X86_FEATURE_TSC)) {
-		setup_clear_cpu_cap(X86_FEATURE_TSC_DEADLINE_TIMER);
-		return;
-	}
-
 	if (!tsc_khz) {
 		/* We failed to determine frequencies earlier, try again */
 		if (!determine_cpu_tsc_frequencies(false)) {
-- 
2.35.1


-- 
Regards/Gruss,
    Boris.

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