linux-kernel - [PATCH v10 16/18] x86/apic: Enable Secure AVIC in Control MSR

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Message-ID: <20250828112126.209028-1-Neeraj.Upadhyay@amd.com>
Date: Thu, 28 Aug 2025 16:51:26 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <linux-kernel@...r.kernel.org>
CC: <bp@...en8.de>, <tglx@...utronix.de>, <mingo@...hat.com>,
	<dave.hansen@...ux.intel.com>, <Thomas.Lendacky@....com>, <nikunj@....com>,
	<Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <David.Kaplan@....com>, <x86@...nel.org>,
	<hpa@...or.com>, <peterz@...radead.org>, <seanjc@...gle.com>,
	<pbonzini@...hat.com>, <kvm@...r.kernel.org>, <huibo.wang@....com>,
	<naveen.rao@....com>, <francescolavra.fl@...il.com>, <tiala@...rosoft.com>
Subject: [PATCH v10 16/18] x86/apic: Enable Secure AVIC in Control MSR

With all the pieces in place now, enable Secure AVIC in Secure
AVIC Control MSR. Any access to x2APIC MSRs are emulated by
the hypervisor before Secure AVIC is enabled in the control MSR.
Post Secure AVIC enablement, all x2APIC MSR accesses (whether
accelerated by AVIC hardware or trapped as VC exception) operate
on vCPU's APIC backing page.

Reviewed-by: Tianyu Lan <tiala@...rosoft.com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
Changes since v9:
 - Rename MSR_AMD64_SECURE_AVIC_EN* macros.

 arch/x86/include/asm/msr-index.h    | 2 ++
 arch/x86/kernel/apic/x2apic_savic.c | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 1291e053e40c..5951344009f1 100644
--- a/arch/x86/include/asm/msr-index.h
+++ b/arch/x86/include/asm/msr-index.h
@@ -704,6 +704,8 @@
 #define MSR_AMD64_SNP_RESV_BIT		19
 #define MSR_AMD64_SNP_RESERVED_MASK	GENMASK_ULL(63, MSR_AMD64_SNP_RESV_BIT)
 #define MSR_AMD64_SAVIC_CONTROL		0xc0010138
+#define MSR_AMD64_SAVIC_EN_BIT		0
+#define MSR_AMD64_SAVIC_EN		BIT_ULL(MSR_AMD64_SAVIC_EN_BIT)
 #define MSR_AMD64_SAVIC_ALLOWEDNMI_BIT	1
 #define MSR_AMD64_SAVIC_ALLOWEDNMI	BIT_ULL(MSR_AMD64_SAVIC_ALLOWEDNMI_BIT)
 #define MSR_AMD64_RMP_BASE		0xc0010132
diff --git a/arch/x86/kernel/apic/x2apic_savic.c b/arch/x86/kernel/apic/x2apic_savic.c
index 88e0ac9ad092..d65282e103c3 100644
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -364,7 +364,8 @@ static void savic_setup(void)
 	res = savic_register_gpa(gpa);
 	if (res != ES_OK)
 		snp_abort();
-	native_wrmsrq(MSR_AMD64_SAVIC_CONTROL, gpa | MSR_AMD64_SAVIC_ALLOWEDNMI);
+	native_wrmsrq(MSR_AMD64_SAVIC_CONTROL,
+		      gpa | MSR_AMD64_SAVIC_EN | MSR_AMD64_SAVIC_ALLOWEDNMI);
 }
 
 static int savic_probe(void)
-- 
2.34.1