linux-kernel - [PATCH 1/3] KVM: x86: hyper-v: Convert synic_auto_eoi

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Message-ID: <3d8ed6be41358c7635bd4e09ecdfd1bc77ce83df.1738595289.git.naveen@kernel.org>
Date: Mon,  3 Feb 2025 22:33:01 +0530
From: "Naveen N Rao (AMD)" <naveen@...nel.org>
To: <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Cc: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
	Vasant Hegde <vasant.hegde@....com>,
	Maxim Levitsky <mlevitsk@...hat.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: [PATCH 1/3] KVM: x86: hyper-v: Convert synic_auto_eoi_used to an atomic

apicv_update_lock is primarily meant for protecting updates to the apicv
state, and is not necessary for guarding updates to synic_auto_eoi_used.
Convert synic_auto_eoi_used to an atomic and use
kvm_set_or_clear_apicv_inhibit() helper to simplify the logic.

Signed-off-by: Naveen N Rao (AMD) <naveen@...nel.org>
---
 arch/x86/include/asm/kvm_host.h |  7 ++-----
 arch/x86/kvm/hyperv.c           | 17 +++++------------
 2 files changed, 7 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 5193c3dfbce1..fb93563714c2 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1150,11 +1150,8 @@ struct kvm_hv {
 	/* How many vCPUs have VP index != vCPU index */
 	atomic_t num_mismatched_vp_indexes;
 
-	/*
-	 * How many SynICs use 'AutoEOI' feature
-	 * (protected by arch.apicv_update_lock)
-	 */
-	unsigned int synic_auto_eoi_used;
+	/* How many SynICs use 'AutoEOI' feature */
+	atomic_t synic_auto_eoi_used;
 
 	struct kvm_hv_syndbg hv_syndbg;
 
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 6a6dd5a84f22..7a4554ea1d16 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -131,25 +131,18 @@ static void synic_update_vector(struct kvm_vcpu_hv_synic *synic,
 	if (auto_eoi_old == auto_eoi_new)
 		return;
 
-	if (!enable_apicv)
-		return;
-
-	down_write(&vcpu->kvm->arch.apicv_update_lock);
-
 	if (auto_eoi_new)
-		hv->synic_auto_eoi_used++;
+		atomic_inc(&hv->synic_auto_eoi_used);
 	else
-		hv->synic_auto_eoi_used--;
+		atomic_dec(&hv->synic_auto_eoi_used);
 
 	/*
 	 * Inhibit APICv if any vCPU is using SynIC's AutoEOI, which relies on
 	 * the hypervisor to manually inject IRQs.
 	 */
-	__kvm_set_or_clear_apicv_inhibit(vcpu->kvm,
-					 APICV_INHIBIT_REASON_HYPERV,
-					 !!hv->synic_auto_eoi_used);
-
-	up_write(&vcpu->kvm->arch.apicv_update_lock);
+	kvm_set_or_clear_apicv_inhibit(vcpu->kvm,
+				       APICV_INHIBIT_REASON_HYPERV,
+				       !!atomic_read(&hv->synic_auto_eoi_used));
 }
 
 static int synic_set_sint(struct kvm_vcpu_hv_synic *synic, int sint,
-- 
2.48.1