linux-kernel - Re: [PATCH 1/1] KVM: x86: ignore SIPIs that are received while not in wait-for-sipi state

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Date:   Thu, 3 Dec 2020 18:36:31 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Joerg Roedel <joro@...tes.org>, Ingo Molnar <mingo@...hat.com>,
        "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Borislav Petkov <bp@...en8.de>,
        Jim Mattson <jmattson@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/1] KVM: x86: ignore SIPIs that are received while not in
 wait-for-sipi state

On 03/12/20 15:33, Maxim Levitsky wrote:
> In the commit 1c96dcceaeb3
> ("KVM: x86: fix apic_accept_events vs check_nested_events"),
> 
> we accidently started latching SIPIs that are received while the cpu is not
> waiting for them.
> 
> This causes vCPUs to never enter a halted state.
> 
> Fixes: 1c96dcceaeb3 ("KVM: x86: fix apic_accept_events vs check_nested_events")
> Signed-off-by: Maxim Levitsky <mlevitsk@...hat.com>
> ---
>  arch/x86/kvm/lapic.c | 15 ++++++++-------


Indeed, it was done by the xchg before that commit, even if 
vcpu->arch.mp_state != KVM_MP_STATE_INIT_RECEIVED.

Paolo