linux-kernel - Re: [PATCH 3/4] KVM: x86: introduce get_kvmclock

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Message-ID: <6207edf3-72e7-229d-8ff7-a91c23e40cd7@redhat.com>
Date:   Fri, 2 Sep 2016 18:57:10 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Roman Kagan <rkagan@...tuozzo.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, peterhornyack@...gle.com, rkrcmar@...hat.com,
        den@...nvz.org
Subject: Re: [PATCH 3/4] KVM: x86: introduce get_kvmclock_ns



On 02/09/2016 18:55, Roman Kagan wrote:
>> > I'll change patch 4 to store the parameters and use them when accessing
>> > the time reference counter MSR.  I'll still keep the procedure that goes
>> > through kvmclock.  It's a bit more involved for the scale, but
>> > vcpu->last_guest_tsc only provides a part of the offset computation; the
>> > other half is vcpu->hv_clock.system_time and it's not stored anywhere.
> Erm... It is stored right there, in vcpu->hv_clock.system_time, you can
> access it just fine when you populate tsc_ref_page values.  Am I missing
> anything?

No.  It's not stored anywhere outside vcpu->hv_clock.  My reasoning goes
that if I have to use vcpu->hv_clock.system_time I might as well use
vcpu->hv_clock for everything. :)

Paolo