linux-kernel - Re: [PATCH v2 0/7] x86/kvm/hyper-v: Implement KVM_GET_SUPPORTED_HV

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Message-ID: <87k1k72qt7.fsf@vitty.brq.redhat.com>
Date:   Tue, 18 Dec 2018 09:16:04 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>, kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        linux-kernel@...r.kernel.org, Roman Kagan <rkagan@...tuozzo.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>, x86@...nel.org,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@...rosoft.com>,
        Eduardo Habkost <ehabkost@...hat.com>
Subject: Re: [PATCH v2 0/7] x86/kvm/hyper-v: Implement KVM_GET_SUPPORTED_HV_CPUID

Paolo Bonzini <pbonzini@...hat.com> writes:

> On 17/12/18 11:30, Vitaly Kuznetsov wrote:
>>> Queued, thanks.  I moved this above the direct EOI series so that
>>> KVM_CAP_HYPERV_STIMER_DIRECT need not exist at any point of the history.
>>>
>> Thanks! Just to make sure (and to conclude our discussion with Roman):
>> with your Qemu maintainer hat on, do you agree with the design decision
>> that KVM_GET_SUPPORTED_HV_CPUID's output value changes when
>> KVM_CAP_HYPERV_ENLIGHTENED_VMCS gets enabled? This differs from
>> KVM_GET_SUPPORTED_CPUID (where we always list all feature bits even if
>> they require explicit enablement)?
>
> It doesn't really matter, since the old capability cannot be removed.
> If you want to change it with a patch on top, that's also okay with me.

Ok, let's leave it as it is: maybe some other userspace (which doesn't
use legacy capabilities) will be grateful :-)

-- 
Vitaly