linux-kernel - Re: [PATCH v2 2/3] KVM: LAPIC: Reset TMCCT during vCPU reset

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Message-ID: <CANRm+Cwee=zwanKQZ1zWA2warRJdp4LVMTn+=uBoWT7-+xm3nQ@mail.gmail.com>
Date:   Wed, 9 Jun 2021 15:18:18 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v2 2/3] KVM: LAPIC: Reset TMCCT during vCPU reset

On Wed, 9 Jun 2021 at 13:52, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 09/06/21 04:15, Wanpeng Li wrote:
> > On Wed, 9 Jun 2021 at 00:27, Paolo Bonzini <pbonzini@...hat.com> wrote:
> > [...]
> >> Perhaps instead set TMCCT to 0 in kvm_apic_set_state, instead of keeping
> >> the value that was filled in by KVM_GET_LAPIC?
> >
> > Keeping the value that was filled in by KVM_GET_LAPIC is introduced by
> > commit 24647e0a39b6 (KVM: x86: Return updated timer current count
> > register from KVM_GET_LAPIC), could you elaborate more? :)
>
> KVM_GET_LAPIC stores the current value of TMCCT and KVM_SET_LAPIC's
> memcpy stores it in vcpu->arch.apic->regs.  KVM_SET_LAPIC perhaps could
> store zero in vcpu->arch.apic->regs after it uses it, and then the
> stored value would always be zero.

Just do it in a new version, thanks. :)

   Wanpeng