linux-kernel - Re: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay

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Message-ID: <CANRm+CzmeoA_zvtr+8QymzGyey4xsr3hBc+S8QBxA5Ad2dQ3=A@mail.gmail.com>
Date:   Thu, 29 Jun 2017 16:17:55 +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 Krčmář <rkrcmar@...hat.com>,
        Wanpeng Li <wanpeng.li@...mail.com>
Subject: Re: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay

2017-06-29 15:55 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>> +
>> +            /* In case the sw timer triggered in the window */
>> +            if (atomic_read(&apic->lapic_timer.pending) &&
>> +                !apic_lvtt_period(apic))
>> +                need_cancel = true;
>> +            else if (r && (apic_lvtt_oneshot(apic) ||
>> apic_lvtt_tscdeadline(apic)))
>> +                apic_timer_expired(apic);
>> +        }
>> +    }

[...]

>
> You still need to enable the preemption timer even if you return 1, so
> in lapic.c it becomes
>
>         if (!apic_lvtt_period(apic)) {
>                 if (r)
>                         apic_timer_expired(apic);
>                 if (atomic_read(&apic->lapic_timer.pending))
>                         need_cancel = true;
>         }

I think the codes are more clear but the same as above. We didn't
program preemption timer vmcs field if delta == 0, so how to
understand "need to enable the preemption timer even if return 1"?

>
>
> Otherwise it looks good.  Thanks for your persistence. :)

Thanks for your help and patient. :)

Regards,
Wanpeng Li