linux-kernel - Re: [PATCH v4 07/10] KVM: x86: remove not used pvclock_gtod

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Date:   Fri, 11 Aug 2017 19:59:12 -0300
From:   Marcelo Tosatti <mtosatti@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Denis Plotnikov <dplotnikov@...tuozzo.com>, rkrcmar@...hat.com,
        kvm@...r.kernel.org, john.stultz@...aro.org, tglx@...utronix.de,
        mingo@...hat.com, hpa@...or.com, linux-kernel@...r.kernel.org,
        x86@...nel.org, rkagan@...tuozzo.com, den@...tuozzo.com
Subject: Re: [PATCH v4 07/10] KVM: x86: remove not used pvclock_gtod_copy

On Thu, Aug 03, 2017 at 02:35:19PM +0200, Paolo Bonzini wrote:
> On 03/08/2017 01:21, Marcelo Tosatti wrote:
> >> -	if (ka->use_master_clock ||
> >> -	    (gtod->clock.vclock_mode == VCLOCK_TSC && vcpus_matched))
> >> +	if (ka->use_master_clock || vcpus_matched)
> >>  		kvm_make_request(KVM_REQ_MASTERCLOCK_UPDATE, vcpu);
> > Don't drop this. The masterclock scheme requires TSC for proper functioning 
> > (or an analysis why its supposed with different HPET+TSC, for example).
> 
> I think testing gtod->clock.vclock_mode is just an optimization?
> kvm_get_time_and_clockread would return false anyway and masterclock
> would not be enabled.
> 
> Paolo

Right.