linux-kernel - [PATCH v7 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available

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Date: Wed, 20 Dec 2023 20:43:55 +0530
From: Nikunj A Dadhania <nikunj@....com>
To: <linux-kernel@...r.kernel.org>, <thomas.lendacky@....com>,
	<x86@...nel.org>, <kvm@...r.kernel.org>
CC: <bp@...en8.de>, <mingo@...hat.com>, <tglx@...utronix.de>,
	<dave.hansen@...ux.intel.com>, <dionnaglaze@...gle.com>, <pgonda@...gle.com>,
	<seanjc@...gle.com>, <pbonzini@...hat.com>, <nikunj@....com>
Subject: [PATCH v7 13/16] x86/kvmclock: Skip kvmclock when Secure TSC is available

For AMD SNP guests having Secure TSC enabled, skip using the kvmclock.
The guest kernel will fallback and use Secure TSC based clocksource.

Signed-off-by: Nikunj A Dadhania <nikunj@....com>
Tested-by: Peter Gonda <pgonda@...gle.com>
---
 arch/x86/kernel/kvmclock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c
index fb8f52149be9..e3de354abf74 100644
--- a/arch/x86/kernel/kvmclock.c
+++ b/arch/x86/kernel/kvmclock.c
@@ -288,7 +288,7 @@ void __init kvmclock_init(void)
 {
 	u8 flags;
 
-	if (!kvm_para_available() || !kvmclock)
+	if (!kvm_para_available() || !kvmclock || cpu_feature_enabled(X86_FEATURE_SNP_SECURE_TSC))
 		return;
 
 	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
-- 
2.34.1