linux-kernel - [PATCH] KVM: x86: zero apic_arb

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Message-Id: <1446216500-14267-1-git-send-email-rkrcmar@redhat.com>
Date:	Fri, 30 Oct 2015 15:48:20 +0100
From:	Radim Krčmář <rkrcmar@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
	Yuki Shibuya <shibuya.yk@...s.nec.co.jp>
Subject: [PATCH] KVM: x86: zero apic_arb_prio on reset

BSP doesn't get INIT so its apic_arb_prio isn't zeroed after reboot.
BSP won't get lowest priority interrupts until other VCPUs get enough
interrupts to match their pre-reboot apic_arb_prio.

That behavior doesn't fit into KVM's round-robin-like interpretation of
lowest priority delivery ... userspace should KVM_SET_LAPIC on reset, so
just zero apic_arb_prio there.

Reported-by: Yuki Shibuya <shibuya.yk@...s.nec.co.jp>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
---
 arch/x86/kvm/lapic.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 1b02c44c7b8b..08655020417d 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1924,6 +1924,8 @@ void kvm_apic_post_state_restore(struct kvm_vcpu *vcpu,
 	kvm_make_request(KVM_REQ_EVENT, vcpu);
 	if (ioapic_in_kernel(vcpu->kvm))
 		kvm_rtc_eoi_tracking_restore_one(vcpu);
+
+	vcpu->arch.apic_arb_prio = 0;
 }
 
 void __kvm_migrate_apic_timer(struct kvm_vcpu *vcpu)
-- 
2.5.3

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