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

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Message-ID: <5b46dad3-a81f-e908-70e5-e7a0f29318d1@redhat.com>
Date:   Thu, 3 Aug 2017 14:35:19 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Marcelo Tosatti <mtosatti@...hat.com>,
        Denis Plotnikov <dplotnikov@...tuozzo.com>
Cc:     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 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