linux-kernel - [RFC 3/3] x86: KVM: stats: Add a stat counter for GALog events

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Date: Thu, 15 Feb 2024 16:01:36 +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,
        joao.m.martins@...cle.com, boris.ostrovsky@...cle.com,
        mark.kanda@...cle.com, suravee.suthikulpanit@....com,
        mlevitsk@...hat.com, alejandro.j.jimenez@...cle.com
Subject: [RFC 3/3] x86: KVM: stats: Add a stat counter for GALog events

Export a per-vCPU binary stat counting GALog events received. Such events
are specific to IOMMU AVIC, and their presence can be used to confirm that
this capability is active. Also, exporting this statistic is useful to
assert that device interrupts are being sent to specific vCPUs, confirming
IRQ affinity settings.

Signed-off-by: Alejandro Jimenez <alejandro.j.jimenez@...cle.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/svm/avic.c         | 4 +++-
 arch/x86/kvm/x86.c              | 1 +
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index b6f18084d504..74e08b57f2e0 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1565,6 +1565,7 @@ struct kvm_vcpu_stat {
 	u64 guest_mode;
 	u64 notify_window_exits;
 	u64 apicv_accept_irq;
+	u64 ga_log_event;
 };
 
 struct x86_instruction_info;
diff --git a/arch/x86/kvm/svm/avic.c b/arch/x86/kvm/svm/avic.c
index 4b74ea91f4e6..853cafe4a9af 100644
--- a/arch/x86/kvm/svm/avic.c
+++ b/arch/x86/kvm/svm/avic.c
@@ -165,8 +165,10 @@ int avic_ga_log_notifier(u32 ga_tag)
 	 * bit in the vAPIC backing page. So, we just need to schedule
 	 * in the vcpu.
 	 */
-	if (vcpu)
+	if (vcpu) {
 		kvm_vcpu_wake_up(vcpu);
+		++vcpu->stat.ga_log_event;
+	}
 
 	return 0;
 }
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2ad70cf6e52c..6a1df29ae650 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -305,6 +305,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
 	STATS_DESC_IBOOLEAN(VCPU, guest_mode),
 	STATS_DESC_COUNTER(VCPU, notify_window_exits),
 	STATS_DESC_COUNTER(VCPU, apicv_accept_irq),
+	STATS_DESC_COUNTER(VCPU, ga_log_event),
 };
 
 const struct kvm_stats_header kvm_vcpu_stats_header = {
-- 
2.39.3