From: Marcelo Tosatti <mtosatti@redhat.com>
To: "Liu, Jinsong" <jinsong.liu@intel.com>
Cc: Avi Kivity <avi@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
"Tian, Kevin" <kevin.tian@intel.com>
Subject: Re: [PATCH 1/2] KVM: emulate lapic tsc deadline timer for guest
Date: Thu, 15 Sep 2011 08:45:31 -0300 [thread overview]
Message-ID: <20110915114531.GA5817@amt.cnet> (raw)
In-Reply-To: <BC00F5384FCFC9499AF06F92E8B78A9E25448A9E6B@shsmsx502.ccr.corp.intel.com>
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.
WARNING: multiple messages have this Message-ID (diff)
From: Marcelo Tosatti <mtosatti@redhat.com>
To: "Liu, Jinsong" <jinsong.liu@intel.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, Avi Kivity <avi@redhat.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>
Subject: Re: [Qemu-devel] [PATCH 1/2] KVM: emulate lapic tsc deadline timer for guest
Date: Thu, 15 Sep 2011 08:45:31 -0300 [thread overview]
Message-ID: <20110915114531.GA5817@amt.cnet> (raw)
In-Reply-To: <BC00F5384FCFC9499AF06F92E8B78A9E25448A9E6B@shsmsx502.ccr.corp.intel.com>
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.
next prev parent reply other threads:[~2011-09-15 11:45 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-13 14:36 [PATCH 1/2] KVM: emulate lapic tsc deadline timer for guest Liu, Jinsong
2011-09-13 14:36 ` [Qemu-devel] " Liu, Jinsong
2011-09-14 11:45 ` Marcelo Tosatti
2011-09-14 11:45 ` [Qemu-devel] " Marcelo Tosatti
2011-09-15 6:22 ` Liu, Jinsong
2011-09-15 6:22 ` [Qemu-devel] " Liu, Jinsong
2011-09-15 12:15 ` Marcelo Tosatti
2011-09-15 12:15 ` [Qemu-devel] " Marcelo Tosatti
2011-09-15 8:17 ` Liu, Jinsong
2011-09-15 8:17 ` [Qemu-devel] " Liu, Jinsong
2011-09-15 11:45 ` Marcelo Tosatti [this message]
2011-09-15 11:45 ` Marcelo Tosatti
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