linux-kernel - [PATCH v9 16/18] x86/apic: Enable Secure AVIC in Control MSR

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Message-ID: <20250811094444.203161-17-Neeraj.Upadhyay@amd.com>
Date: Mon, 11 Aug 2025 15:14:42 +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>,
	<kirill.shutemov@...ux.intel.com>, <huibo.wang@....com>,
	<naveen.rao@....com>, <francescolavra.fl@...il.com>, <tiala@...rosoft.com>
Subject: [PATCH v9 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 v8:
 - Added Tianyu's Reviewed-by.

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

diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
index 2efc03d324c0..3d0688af2009 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_SECURE_AVIC_CONTROL	0xc0010138
+#define MSR_AMD64_SECURE_AVIC_EN_BIT	0
+#define MSR_AMD64_SECURE_AVIC_EN	BIT_ULL(MSR_AMD64_SECURE_AVIC_EN_BIT)
 #define MSR_AMD64_SECURE_AVIC_ALLOWEDNMI_BIT 1
 #define MSR_AMD64_SECURE_AVIC_ALLOWEDNMI BIT_ULL(MSR_AMD64_SECURE_AVIC_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 71775d6d8fbe..e3d8a4302522 100644
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -360,7 +360,7 @@ static void savic_setup(void)
 	res = savic_register_gpa(gpa);
 	if (res != ES_OK)
 		snp_abort();
-	savic_wr_control_msr(gpa | MSR_AMD64_SECURE_AVIC_ALLOWEDNMI);
+	savic_wr_control_msr(gpa | MSR_AMD64_SECURE_AVIC_EN | MSR_AMD64_SECURE_AVIC_ALLOWEDNMI);
 }
 
 static int savic_probe(void)
-- 
2.34.1