linux-kernel - Re: [PATCH RFC 3/6] KVM: x86: interrupt based APF page-ready event delivery

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Message-ID: <546bb75a-ec00-f748-1f44-2b5299a3d3d7@redhat.com>
Date:   Wed, 29 Apr 2020 12:54:38 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, x86@...nel.org,
        kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>
Subject: Re: [PATCH RFC 3/6] KVM: x86: interrupt based APF page-ready event
 delivery

On 29/04/20 11:36, Vitaly Kuznetsov wrote:
> +
> +	Type 1 page (page missing) events are currently always delivered as
> +	synthetic #PF exception. Type 2 (page ready) are either delivered
> +	by #PF exception (when bit 3 of MSR_KVM_ASYNC_PF_EN is clear) or
> +	via an APIC interrupt (when bit 3 set). APIC interrupt delivery is
> +	controlled by MSR_KVM_ASYNC_PF2.

I think we should (in the non-RFC version) block async page faults
completely and only keep APF_HALT unless the guest is using page ready
interrupt delivery.

Paolo