linux-kernel - Re: [PATCH 2/8] KVM: x86: extend struct kvm_vcpu_pv_apf

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Message-ID: <874kskmcak.fsf@vitty.brq.redhat.com>
Date:   Wed, 13 May 2020 11:09:23 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vivek Goyal <vgoyal@...hat.com>
Cc:     kvm@...r.kernel.org, x86@...nel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Gavin Shan <gshan@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/8] KVM: x86: extend struct kvm_vcpu_pv_apf_data with token info

Sean Christopherson <sean.j.christopherson@...el.com> writes:

>
> Why bother preserving backwards compatibility?  AIUI, both KVM and guest
> will support async #PF iff interrupt delivery is enabled.  Why not make
> the interrupt delivery approach KVM_ASYNC_PF_V2 and completely redefine the
> ABI?  E.g. to make it compatible with reflecting !PRESENT faults without a
> VM-Exit via Intel's EPT Violation #VE?
>

That's the plan, actually. 'page not present' becomes #VE and 'page
present' becomes an interrupt (we don't need to inject them
synchronously). These two parts are fairly independent but can be merged
to reuse the same new capability/CPUID.

-- 
Vitaly