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

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Message-ID: <56374F98.4050502@redhat.com>
Date:	Mon, 2 Nov 2015 12:57:12 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>,
	linux-kernel@...r.kernel.org
Cc:	kvm@...r.kernel.org, Yuki Shibuya <shibuya.yk@...s.nec.co.jp>
Subject: Re: [PATCH] KVM: x86: zero apic_arb_prio on reset



On 30/10/2015 15:48, Radim Krčmář wrote:
> 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)
> 

Applied, thanks.

Paolo
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