linux-kernel - [PATCH v2 2/2] KVM: LAPIC: Don't need to clear IPI delivery status in x2apic mode

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Message-Id: <1585700362-11892-2-git-send-email-wanpengli@tencent.com>
Date:   Wed,  1 Apr 2020 08:19:22 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: [PATCH v2 2/2] KVM: LAPIC: Don't need to clear IPI delivery status in x2apic mode

From: Wanpeng Li <wanpengli@...cent.com>

IPI delivery status field is not present in x2apic mode, don't need 
to clear IPI delivery status in x2apic mode.

Reviewed-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
---
v1 -> v2:
 * update code comments
 * update subject and patch description

 arch/x86/kvm/lapic.c | 5 +++--
 arch/x86/kvm/x86.c   | 1 -
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index d528bed..5efca58 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1941,8 +1941,9 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
 		break;
 	}
 	case APIC_ICR:
-		/* No delay here, so we always clear the pending bit */
-		val &= ~(1 << 12);
+		/* Immediately clear Delivery Status in xAPIC mode */
+		if (!apic_x2apic_mode(apic))
+			val &= ~(1 << 12);
 		kvm_apic_send_ipi(apic, val, kvm_lapic_get_reg(apic, APIC_ICR2));
 		kvm_lapic_set_reg(apic, APIC_ICR, val);
 		break;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5a645df..ececc09 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1562,7 +1562,6 @@ static int handle_fastpath_set_x2apic_icr_irqoff(struct kvm_vcpu *vcpu, u64 data
 		((data & APIC_MODE_MASK) == APIC_DM_FIXED) &&
 		((u32)(data >> 32) != X2APIC_BROADCAST)) {
 
-		data &= ~(1 << 12);
 		kvm_apic_send_ipi(vcpu->arch.apic, (u32)data, (u32)(data >> 32));
 		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR2, (u32)(data >> 32));
 		kvm_lapic_set_reg(vcpu->arch.apic, APIC_ICR, (u32)data);
-- 
2.7.4