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From: Nikunj A Dadhania <nikunj@amd.com>
To: <linux-kernel@vger.kernel.org>, <thomas.lendacky@amd.com>, <bp@alien8.de>,
	<x86@kernel.org>, <kvm@vger.kernel.org>
CC: <mingo@redhat.com>, <tglx@linutronix.de>, <dave.hansen@linux.intel.com>,
	<pgonda@google.com>, <seanjc@google.com>, <pbonzini@redhat.com>,
	<nikunj@amd.com>
Subject: [PATCH v8 14/16] x86/sev: Mark Secure TSC as reliable
Date: Thu, 15 Feb 2024 17:01:26 +0530
Message-ID: <20240215113128.275608-15-nikunj@amd.com>
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AMD SNP guests may have Secure TSC feature enabled. Use the Secure TSC
as the only reliable clock source in SEV-SNP guests when enabled,
bypassing unstable calibration.

Signed-off-by: Nikunj A Dadhania <nikunj@amd.com>
Tested-by: Peter Gonda <pgonda@google.com>
---
 arch/x86/mm/mem_encrypt_amd.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
index c81b57ca03b6..cc936999efc8 100644
--- a/arch/x86/mm/mem_encrypt_amd.c
+++ b/arch/x86/mm/mem_encrypt_amd.c
@@ -498,6 +498,10 @@ void __init sme_early_init(void)
 	 */
 	if (sev_status & MSR_AMD64_SEV_ENABLED)
 		ia32_disable();
+
+	/* Mark the TSC as reliable when Secure TSC is enabled */
+	if (sev_status & MSR_AMD64_SNP_SECURE_TSC)
+		setup_force_cpu_cap(X86_FEATURE_TSC_RELIABLE);
 }
 
 void __init mem_encrypt_free_decrypted_mem(void)
-- 
2.34.1