From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752651AbdF2LnU (ORCPT <rfc822;w@1wt.eu>);
        Thu, 29 Jun 2017 07:43:20 -0400
Received: from mail-wm0-f68.google.com ([74.125.82.68]:33480 "EHLO
        mail-wm0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751837AbdF2LnK (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Thu, 29 Jun 2017 07:43:10 -0400
Subject: Re: [PATCH v3] KVM: LAPIC: Fix lapic timer injection delay
To: Wanpeng Li <kernellwp@gmail.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        kvm <kvm@vger.kernel.org>,
        =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        Wanpeng Li <wanpeng.li@hotmail.com>
References: <1498613352-4651-1-git-send-email-wanpeng.li@hotmail.com>
 <68c0d7f8-683f-c7fa-b328-e90e8dd9a789@redhat.com>
 <CANRm+CwMcVwUqyj_3-LGBFdjKXe-7U=KVi=-rNZCR5kJZX+VOw@mail.gmail.com>
 <6fc8f133-15b8-3ee2-1483-614642deffa0@redhat.com>
 <CANRm+CzcfwQg=0dJzGD8E4d+ay-eMZz+xTpVEZFSwugF-epNyA@mail.gmail.com>
 <62c6b468-52c0-38c5-e15f-c770483188cd@redhat.com>
 <CANRm+CzmeoA_zvtr+8QymzGyey4xsr3hBc+S8QBxA5Ad2dQ3=A@mail.gmail.com>
 <CANRm+CyYiSAn+HnaDY=qJAx6HRFsKVyWmuUpQr50f1CaQQjVew@mail.gmail.com>
From: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <b23e1e52-4dae-201f-3be5-00d79c06d62c@redhat.com>
Date: Thu, 29 Jun 2017 13:43:05 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.2.0
MIME-Version: 1.0
In-Reply-To: <CANRm+CyYiSAn+HnaDY=qJAx6HRFsKVyWmuUpQr50f1CaQQjVew@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



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.

Paolo