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

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Message-ID: <20be1e98-deec-ea00-32e1-251781a35f83@redhat.com>
Date:   Mon, 3 Jul 2017 09:30:19 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.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



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.

Paolo