linux-kernel - [RFC PATCH v2 03/17] KVM: SVM: Add support for Secure AVIC capability in KVM

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Message-ID: <20250923050317.205482-4-Neeraj.Upadhyay@amd.com>
Date: Tue, 23 Sep 2025 10:33:03 +0530
From: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
To: <kvm@...r.kernel.org>, <seanjc@...gle.com>, <pbonzini@...hat.com>
CC: <linux-kernel@...r.kernel.org>, <Thomas.Lendacky@....com>,
	<nikunj@....com>, <Santosh.Shukla@....com>, <Vasant.Hegde@....com>,
	<Suravee.Suthikulpanit@....com>, <bp@...en8.de>, <David.Kaplan@....com>,
	<huibo.wang@....com>, <naveen.rao@....com>, <tiala@...rosoft.com>
Subject: [RFC PATCH v2 03/17] KVM: SVM: Add support for Secure AVIC capability in KVM

Add support to KVM for determining if a system is capable of supporting
Secure AVIC feature.

Secure AVIC feature support is determined based on:

- secure_avic module parameter is set.
- X86_FEATURE_SECURE_AVIC CPU feature bit is set.
- SNP feature is supported.

Co-developed-by: Kishon Vijay Abraham I <kvijayab@....com>
Signed-off-by: Kishon Vijay Abraham I <kvijayab@....com>
Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
---
 arch/x86/include/asm/svm.h | 1 +
 arch/x86/kvm/svm/sev.c     | 9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h
index ffc27f676243..ab3d55654c77 100644
--- a/arch/x86/include/asm/svm.h
+++ b/arch/x86/include/asm/svm.h
@@ -299,6 +299,7 @@ static_assert((X2AVIC_MAX_PHYSICAL_ID & AVIC_PHYSICAL_MAX_INDEX_MASK) == X2AVIC_
 #define SVM_SEV_FEAT_RESTRICTED_INJECTION		BIT(3)
 #define SVM_SEV_FEAT_ALTERNATE_INJECTION		BIT(4)
 #define SVM_SEV_FEAT_DEBUG_SWAP				BIT(5)
+#define SVM_SEV_FEAT_SECURE_AVIC			BIT(16)
 
 #define VMCB_ALLOWED_SEV_FEATURES_VALID			BIT_ULL(63)
 
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 5bac4d20aec0..b2eae102681c 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -59,6 +59,10 @@ static bool sev_es_debug_swap_enabled = true;
 module_param_named(debug_swap, sev_es_debug_swap_enabled, bool, 0444);
 static u64 sev_supported_vmsa_features;
 
+/* enable/disable SEV-SNP Secure AVIC support */
+bool sev_snp_savic_enabled = true;
+module_param_named(secure_avic, sev_snp_savic_enabled, bool, 0444);
+
 #define AP_RESET_HOLD_NONE		0
 #define AP_RESET_HOLD_NAE_EVENT		1
 #define AP_RESET_HOLD_MSR_PROTO		2
@@ -2911,6 +2915,8 @@ void __init sev_set_cpu_caps(void)
 		kvm_cpu_cap_set(X86_FEATURE_SEV_SNP);
 		kvm_caps.supported_vm_types |= BIT(KVM_X86_SNP_VM);
 	}
+	if (sev_snp_savic_enabled)
+		kvm_cpu_cap_set(X86_FEATURE_SECURE_AVIC);
 }
 
 static bool is_sev_snp_initialized(void)
@@ -3075,6 +3081,9 @@ void __init sev_hardware_setup(void)
 	    !cpu_feature_enabled(X86_FEATURE_NO_NESTED_DATA_BP))
 		sev_es_debug_swap_enabled = false;
 
+	if (!sev_snp_supported || !cpu_feature_enabled(X86_FEATURE_SECURE_AVIC))
+		sev_snp_savic_enabled = false;
+
 	sev_supported_vmsa_features = 0;
 	if (sev_es_debug_swap_enabled)
 		sev_supported_vmsa_features |= SVM_SEV_FEAT_DEBUG_SWAP;
-- 
2.34.1