linux-kernel - Re: [PATCH 3/3] KVM: LAPIC: Fix lapic timer injection delay

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Message-ID: <CANRm+CwCreBC_EErbTa98dvtNzj5tzHDm1=zNozAGkVLoEXSUQ@mail.gmail.com>
Date:   Mon, 3 Jul 2017 16:08:25 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        kvm <kvm@...r.kernel.org>, Radim Krcmar <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH 3/3] KVM: LAPIC: Fix lapic timer injection delay

2017-07-03 15:30 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>
>
> On 02/07/2017 03:56, Wanpeng Li wrote:
>>>> -       if (!apic_lvtt_period(apic) && atomic_read(&ktimer->pending))
>>>> +       if (!apic_lvtt_period(apic) && (r || atomic_read(&ktimer->pending))) {
>>>> +               if (r)
>>>> +                       apic_timer_expired(apic);
>>>>                 return false;
>>>> +       }
>>>
>>> This logic is not the same as in my v4
>>> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1434040.html
>>> . You return false for the expired timer and actually it will switch
>>> to sw timer.
>>
>> Ah, I miss read it, the rebase is correct.
>
> Yeah, I'm not entirely satisfied with it but it's working: start_sw
> timer will see ktimer->pending and do nothing.
>
> But thinking more about it, maybe the "if (r)" can be omitted
> completely?  We need to benchmark it but it can be done.

"if (r)" makes codes more understandable, in addition, calling expired
the pending timer here looks weird though ktimer->pending.

Regards,
Wanpeng Li