linux-kernel - [PATCH v13 06/13] x86/sev: Prevent GUEST_TSC_FREQ MSR interception for Secure TSC enabled guests

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Message-ID: <20241021055156.2342564-7-nikunj@amd.com>
Date: Mon, 21 Oct 2024 11:21:49 +0530
From: Nikunj A Dadhania <nikunj@....com>
To: <linux-kernel@...r.kernel.org>, <thomas.lendacky@....com>, <bp@...en8.de>,
	<x86@...nel.org>, <kvm@...r.kernel.org>
CC: <mingo@...hat.com>, <tglx@...utronix.de>, <dave.hansen@...ux.intel.com>,
	<pgonda@...gle.com>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
	<nikunj@....com>
Subject: [PATCH v13 06/13] x86/sev: Prevent GUEST_TSC_FREQ MSR interception for Secure TSC enabled guests

The hypervisor should not be intercepting GUEST_TSC_FREQ MSR(0xcOO10134)
when Secure TSC is enabled. A #VC exception will be generated if the
GUEST_TSC_FREQ MSR is being intercepted. If this should occur and SecureTSC
is enabled, terminate guest execution.

Signed-off-by: Nikunj A Dadhania <nikunj@....com>
---
 arch/x86/include/asm/msr-index.h | 1 +
 arch/x86/coco/sev/core.c         | 8 ++++++++
 2 files changed, 9 insertions(+)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 3ae84c3b8e6d..233be13cc21f 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -608,6 +608,7 @@
 #define MSR_AMD_PERF_CTL		0xc0010062
 #define MSR_AMD_PERF_STATUS		0xc0010063
 #define MSR_AMD_PSTATE_DEF_BASE		0xc0010064
+#define MSR_AMD64_GUEST_TSC_FREQ	0xc0010134
 #define MSR_AMD64_OSVW_ID_LENGTH	0xc0010140
 #define MSR_AMD64_OSVW_STATUS		0xc0010141
 #define MSR_AMD_PPIN_CTL		0xc00102f0
diff --git a/arch/x86/coco/sev/core.c b/arch/x86/coco/sev/core.c
index 2ad7773458c0..4e9b1cc1f26b 100644
--- a/arch/x86/coco/sev/core.c
+++ b/arch/x86/coco/sev/core.c
@@ -1332,6 +1332,14 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 		return ES_OK;
 	}
 
+	/*
+	 * GUEST_TSC_FREQ should not be intercepted when Secure TSC is
+	 * enabled. Terminate the SNP guest when the interception is enabled.
+	 */
+	if (regs->cx == MSR_AMD64_GUEST_TSC_FREQ && cc_platform_has(CC_ATTR_GUEST_SNP_SECURE_TSC))
+		return ES_VMM_ERROR;
+
+
 	ghcb_set_rcx(ghcb, regs->cx);
 	if (exit_info_1) {
 		ghcb_set_rax(ghcb, regs->ax);
-- 
2.34.1