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

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Message-ID: <CANRm+CyjQk377z32+jusQ7k7H7+a3-QN4jThHBPnT4RFEpzjSA@mail.gmail.com>
Date:   Thu, 29 Jun 2017 19:54:24 +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 19:43 GMT+08:00 Paolo Bonzini <pbonzini@...hat.com>:
>
>
> On 29/06/2017 10:44, Wanpeng Li wrote:
>>>> 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"?
>> I guess you mean start_hv_timer() should return true, right?
>
> vmx.c's set_hv_timer callback should set the preemption timer execution
> control.  Otherwise, kvm_lapic_hv_timer_expired is again not called.

I see, this should be set for apic timer periodic mode.

Regards,
Wanpeng Li