linux-kernel - [PATCH 1/4] KVM: x86: Expose per-vCPU APICv status

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Date: Mon, 29 Apr 2024 15:57:35 +0000
From: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
To: kvm@...r.kernel.org
Cc: seanjc@...gle.com, pbonzini@...hat.com, linux-kernel@...r.kernel.org,
        suravee.suthikulpanit@....com, vashegde@....com, mlevitsk@...hat.com,
        joao.m.martins@...cle.com, boris.ostrovsky@...cle.com,
        mark.kanda@...cle.com, alejandro.j.jimenez@...cle.com
Subject: [PATCH 1/4] KVM: x86: Expose per-vCPU APICv status

Expose the APICv activation status of individual vCPUs via the stats
subsystem. In special cases a vCPU's APICv can be deactivated/disabled
even though there are no VM-wide inhibition reasons. The only current
example of this is AVIC for a vCPU running in nested mode. This type of
inhibition is not recorded in the VM inhibit reasons or visible in
current tracepoints.

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/lapic.c            | 1 +
 arch/x86/kvm/x86.c              | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 1d13e3cd1dc5..12f30cb5c842 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1573,6 +1573,7 @@ struct kvm_vcpu_stat {
 	u64 preemption_other;
 	u64 guest_mode;
 	u64 notify_window_exits;
+	u64 apicv_active;
 };
 
 struct x86_instruction_info;
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index cf37586f0466..37fe75a5db8c 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2872,6 +2872,7 @@ int kvm_create_lapic(struct kvm_vcpu *vcpu, int timer_advance_ns)
 	 */
 	if (enable_apicv) {
 		apic->apicv_active = true;
+		vcpu->stat.apicv_active = apic->apicv_active;
 		kvm_make_request(KVM_REQ_APICV_UPDATE, vcpu);
 	}
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e9ef1fa4b90b..0451c4c8d731 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -304,6 +304,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
 	STATS_DESC_COUNTER(VCPU, preemption_other),
 	STATS_DESC_IBOOLEAN(VCPU, guest_mode),
 	STATS_DESC_COUNTER(VCPU, notify_window_exits),
+	STATS_DESC_IBOOLEAN(VCPU, apicv_active),
 };
 
 const struct kvm_stats_header kvm_vcpu_stats_header = {
@@ -10625,6 +10626,7 @@ void __kvm_vcpu_update_apicv(struct kvm_vcpu *vcpu)
 		goto out;
 
 	apic->apicv_active = activate;
+	vcpu->stat.apicv_active = apic->apicv_active;
 	kvm_apic_update_apicv(vcpu);
 	static_call(kvm_x86_refresh_apicv_exec_ctrl)(vcpu);
 
-- 
2.39.3