[tip: x86/apic] x86/apic: Enable Secure AVIC in the control MSR

["tip-bot2 for Neeraj Upadhyay" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/apic branch of tip:

Commit-ID:     c4074ab87f3483deb15f277f302f199cdb997738
Gitweb:        https://git.kernel.org/tip/c4074ab87f3483deb15f277f302f199cdb997738
Author:        Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
AuthorDate:    Thu, 28 Aug 2025 16:51:26 +05:30
Committer:     Borislav Petkov (AMD) <bp@alien8.de>
CommitterDate: Mon, 01 Sep 2025 13:18:14 +02:00

x86/apic: Enable Secure AVIC in the control MSR

With all the pieces in place now, enable Secure AVIC in the 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 a #VC exception) operate on the vCPU's APIC
backing page.

Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Tianyu Lan <tiala@microsoft.com>
Link: https://lore.kernel.org/20250828112126.209028-1-Neeraj.Upadhyay@amd.com
---
 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 1291e05..5951344 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 36e6d0d..b846de0 100644
--- a/arch/x86/kernel/apic/x2apic_savic.c
+++ b/arch/x86/kernel/apic/x2apic_savic.c
@@ -365,7 +365,8 @@ static void savic_setup(void)
 	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)