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

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Message-ID: <CANRm+CxmyhcxPZRLOt9aTf=mT6wCiq9sJ16Ani0P4bizzEMscw@mail.gmail.com>
Date:   Mon, 3 Jul 2017 16:41:48 +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 16:16 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>
>
> On 03/07/2017 10:08, Wanpeng Li wrote:
>>> 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.
>
> We can remove the call to apic_timer_expired too (sorry if I was too
> terse). :)  start_sw_period and start_sw_tscdeadline would take care of it.

IRQ disable and ktime_get() in start_sw_tscdeadline() are more
expensive. So maybe current status is a better choice. :)

Regards,
Wanpeng Li