From: Paolo Bonzini <pbonzini@redhat.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>,
Eduardo Habkost <ehabkost@redhat.com>,
Marcelo Tosatti <mtosatti@redhat.com>,
Roman Kagan <rkagan@virtuozzo.com>,
qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure
Date: Fri, 16 Mar 2018 16:28:20 +0100 [thread overview]
Message-ID: <cd71ecd6-7a3c-05e5-7854-d71763cbc4c2@redhat.com> (raw)
In-Reply-To: <87efkk9i2j.fsf@vitty.brq.redhat.com>
On 16/03/2018 16:05, Vitaly Kuznetsov wrote:
>>>
>>> - if (has_msr_hv_frequencies && tsc_is_stable_and_known(env)) {
>>> + if (has_msr_hv_frequencies && env->tsc_khz) {
>> Should this be
>>
>> ((env->tsc_khz && has_msr_hv_reenlightenment) ||
>> tsc_is_stable_and_known(env))
>>
>> so that you don't regress on older kernels?
>>
> I don't actually see where the regression might come from: frequency
> MSRs are supported regardless or reenlightenment/invtsc and there's
> nothing wrong with exposing them but I may be missing something..
On older kernel without re-enlightenment support, you don't want to
expose the frequency MSRs unless invtsc is on, right?
Paolo
next prev parent reply other threads:[~2018-03-16 15:28 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-03-12 15:12 [Qemu-devel] [PATCH 0/2] i386/kvm: TSC page clocksource for Hyper-V-on-KVM fixes Vitaly Kuznetsov
2018-03-12 15:12 ` [Qemu-devel] [PATCH 1/2] i386/kvm: add support for Hyper-V reenlightenment MSRs Vitaly Kuznetsov
2018-03-16 14:48 ` Paolo Bonzini
2018-03-16 15:10 ` Vitaly Kuznetsov
2018-03-12 15:12 ` [Qemu-devel] [PATCH 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure Vitaly Kuznetsov
2018-03-16 14:49 ` Paolo Bonzini
2018-03-16 15:05 ` Vitaly Kuznetsov
2018-03-16 15:28 ` Paolo Bonzini [this message]
2018-03-16 15:40 ` Vitaly Kuznetsov
2018-03-16 16:04 ` Paolo Bonzini
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