From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marcelo Tosatti Subject: Re: [PATCH 1/2] KVM: emulate lapic tsc deadline timer for guest Date: Thu, 15 Sep 2011 08:45:31 -0300 Message-ID: <20110915114531.GA5817@amt.cnet> References: <20110914114530.GA20351@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Avi Kivity , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" , "Tian, Kevin" To: "Liu, Jinsong" Return-path: Received: from mx1.redhat.com ([209.132.183.28]:12685 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933075Ab1IOLpy (ORCPT ); Thu, 15 Sep 2011 07:45:54 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Thu, Sep 15, 2011 at 04:17:20PM +0800, Liu, Jinsong wrote: > Marcelo Tosatti wrote: > >> + } else if (apic_lvtt_tscdeadline(apic)) { > >> + /* lapic timer in tsc deadline mode */ > >> + u64 guest_tsc, guest_tsc_delta, ns = 0; > >> + struct kvm_vcpu *vcpu = apic->vcpu; > >> + unsigned long this_tsc_khz = vcpu_tsc_khz(vcpu); + unsigned long > >> flags; + > >> + if (unlikely(!apic->lapic_timer.tscdeadline || !this_tsc_khz)) > >> + return; + > >> + local_irq_save(flags); > >> + > >> + now = apic->lapic_timer.timer.base->get_time(); > >> + kvm_get_msr(vcpu, MSR_IA32_TSC, &guest_tsc); > > > > Use kvm_x86_ops->read_l1_tsc(vcpu) instead of direct MSR read > > (to avoid reading L2 guest TSC in case of nested virt). > > > >> + guest_tsc_delta = apic->lapic_timer.tscdeadline - guest_tsc; > > > > if (guest_tsc <= tscdeadline), the timer should start immediately. > > > > Yes, under such case the timer does start immediately, with ns = 0 No, guest_tsc_delta is unsigned, so the "< 0" comparation fails.