linux-kernel - [PATCH v4 2/7] KVM: SVM: Add a helper to look up the max physical ID for AVIC

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <82992eac8f3a2424373001d76526f418276532a5.1755797611.git.naveen@kernel.org>
Date: Thu, 21 Aug 2025 23:48:33 +0530
From: "Naveen N Rao (AMD)" <naveen@...nel.org>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Cc: <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Vasant Hegde <vasant.hegde@....com>,
	Pankaj Gupta <pankaj.gupta@....com>,
	Alejandro Jimenez <alejandro.j.jimenez@...cle.com>,
	Joao Martins <joao.m.martins@...cle.com>,
	Nikunj A Dadhania <nikunj@....com>
Subject: [PATCH v4 2/7] KVM: SVM: Add a helper to look up the max physical ID for AVIC

To help with a future change, add a helper to look up the maximum
physical ID depending on the vCPU AVIC mode. No functional change
intended.

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Naveen N Rao (AMD) <naveen@...nel.org>
---
 arch/x86/kvm/svm/avic.c | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index a6908ac5298d..4f00e31347c3 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -79,13 +79,31 @@ static bool next_vm_id_wrapped = 0;
 static DEFINE_SPINLOCK(svm_vm_data_hash_lock);
 bool x2avic_enabled;
 
+static u32 avic_get_max_physical_id(struct kvm_vcpu *vcpu)
+{
+	u32 arch_max;
+
+	if (x2avic_enabled && apic_x2apic_mode(vcpu->arch.apic))
+		arch_max = X2AVIC_MAX_PHYSICAL_ID;
+	else
+		arch_max = AVIC_MAX_PHYSICAL_ID;
+
+	/*
+	 * Despite its name, KVM_CAP_MAX_VCPU_ID represents the maximum APIC ID plus one,
+	 * so the max possible APIC ID is one less than that.
+	 */
+	return min(vcpu->kvm->arch.max_vcpu_ids - 1, arch_max);
+}
+
 static void avic_activate_vmcb(struct vcpu_svm *svm)
 {
 	struct vmcb *vmcb = svm->vmcb01.ptr;
-	struct kvm *kvm = svm->vcpu.kvm;
+	struct kvm_vcpu *vcpu = &svm->vcpu;
 
 	vmcb->control.int_ctl &= ~(AVIC_ENABLE_MASK | X2APIC_MODE_MASK);
+
 	vmcb->control.avic_physical_id &= ~AVIC_PHYSICAL_MAX_INDEX_MASK;
+	vmcb->control.avic_physical_id |= avic_get_max_physical_id(vcpu);
 
 	vmcb->control.int_ctl |= AVIC_ENABLE_MASK;
 
@@ -98,8 +116,7 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 	 */
 	if (x2avic_enabled && apic_x2apic_mode(svm->vcpu.arch.apic)) {
 		vmcb->control.int_ctl |= X2APIC_MODE_MASK;
-		vmcb->control.avic_physical_id |= min(kvm->arch.max_vcpu_ids - 1,
-						      X2AVIC_MAX_PHYSICAL_ID);
+
 		/* Disabling MSR intercept for x2APIC registers */
 		svm_set_x2apic_msr_interception(svm, false);
 	} else {
@@ -109,9 +126,6 @@ static void avic_activate_vmcb(struct vcpu_svm *svm)
 		 */
 		kvm_make_request(KVM_REQ_TLB_FLUSH_CURRENT, &svm->vcpu);
 
-		/* For xAVIC and hybrid-xAVIC modes */
-		vmcb->control.avic_physical_id |= min(kvm->arch.max_vcpu_ids - 1,
-						      AVIC_MAX_PHYSICAL_ID);
 		/* Enabling MSR intercept for x2APIC registers */
 		svm_set_x2apic_msr_interception(svm, true);
 	}
-- 
2.50.1