From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Vadim Rozenfeld <vrozenfe@redhat.com>, kvm@vger.kernel.org, pl@dlhnet.de
Subject: Re: [RFC PATCH v3 2/2] add support for Hyper-V partition reference time enlightenment
Date: Thu, 12 Dec 2013 10:34:06 +0100 [thread overview]
Message-ID: <52A9830E.4020102@redhat.com> (raw)
In-Reply-To: <20131211192700.GA28701@amt.cnet>
Il 11/12/2013 20:27, Marcelo Tosatti ha scritto:
>> > + if (kvm->arch.hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) {
>> > + HV_REFERENCE_TSC_PAGE* tsc_ref;
>> > + tsc_ref = (HV_REFERENCE_TSC_PAGE*)gfn_to_hva(kvm,
>> > + kvm->arch.hv_tsc_page >> HV_X64_MSR_TSC_REFERENCE_ADDRESS_SHIFT);
> kvm_read_guest_cached.
>
>> > + kvm->arch.hv_ref_time = (((tsc_ref->tsc_scale >> 32) *
>> > + native_read_tsc()) >> 32) + tsc_ref->tsc_offset;
> Why native_read_tsc and not ->read_l1_tsc?
>
> It is easier to trust on the host to check reliability of the TSC: if
> it uses TSC clocksource, then the TSCs are stable. So could condition
> exposing the TSC ref page when ka->use_master_clock=1, see kvm_guest_time_update.
> And hook into pvclock_gtod_notify.
>
> So in addition to X86_FEATURE_CONSTANT_TSC, check
> ka->use_master_clock=1
FWIW, I agree with all these comments from Marcelo.
Paolo
next prev parent reply other threads:[~2013-12-12 9:34 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-08 11:33 [RFC PATCH v3 0/2] Hyper-V timers Vadim Rozenfeld
2013-12-08 11:33 ` [RFC PATCH v3 1/2] add support for Hyper-V reference time counter Vadim Rozenfeld
2013-12-09 14:23 ` Paolo Bonzini
2013-12-10 10:46 ` Vadim Rozenfeld
2013-12-11 18:53 ` Marcelo Tosatti
2013-12-11 18:59 ` Marcelo Tosatti
2013-12-12 9:33 ` Paolo Bonzini
2014-01-02 16:52 ` Peter Lieven
2014-01-07 9:36 ` Vadim Rozenfeld
2014-01-07 17:52 ` Peter Lieven
2014-01-08 9:40 ` Vadim Rozenfeld
2014-01-08 10:15 ` Peter Lieven
2014-01-08 10:44 ` Vadim Rozenfeld
2014-01-08 11:48 ` Peter Lieven
2014-01-08 12:12 ` Vadim Rozenfeld
2014-01-08 14:54 ` Peter Lieven
2014-01-08 20:08 ` Vadim Rozenfeld
2014-01-08 22:20 ` Peter Lieven
2014-01-09 11:10 ` Vadim Rozenfeld
2014-01-12 12:08 ` Vadim Rozenfeld
2014-01-12 20:35 ` Peter Lieven
2014-01-02 13:15 ` Peter Lieven
2014-01-02 13:57 ` Marcelo Tosatti
2014-01-02 16:08 ` Peter Lieven
2014-01-02 20:05 ` Marcelo Tosatti
2014-01-13 12:10 ` Vadim Rozenfeld
2013-12-08 11:33 ` [RFC PATCH v3 2/2] add support for Hyper-V partition reference time enlightenment Vadim Rozenfeld
2013-12-09 14:32 ` Paolo Bonzini
2013-12-10 11:23 ` Vadim Rozenfeld
2013-12-10 16:52 ` Paolo Bonzini
2013-12-11 10:58 ` Vadim Rozenfeld
2013-12-11 12:28 ` Paolo Bonzini
2013-12-11 19:28 ` Marcelo Tosatti
2013-12-11 19:27 ` Marcelo Tosatti
2013-12-12 9:34 ` Paolo Bonzini [this message]
2014-01-14 4:11 ` Vadim Rozenfeld
2014-01-14 13:54 ` Marcelo Tosatti
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