linux-kernel - Re: [RFC PATCH v3 2/2] KVM: x86: Allow Qemu/KVM to use PVH entry point

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Message-ID: <72846976-b3c3-ceca-8168-d50bcad5993e@redhat.com>
Date:   Fri, 15 Dec 2017 18:25:34 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Juergen Gross <jgross@...e.com>,
        Maran Wilson <maran.wilson@...cle.com>,
        boris.ostrovsky@...cle.com, roger.pau@...rix.com,
        andrew.cooper3@...rix.com, hch@...radead.org, JBeulich@...e.com,
        x86@...nel.org, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        rkrcmar@...hat.com
Subject: Re: [RFC PATCH v3 2/2] KVM: x86: Allow Qemu/KVM to use PVH entry
 point

On 15/12/2017 16:55, Juergen Gross wrote:
> I'm fine with the general idea.
> 
> I'm wondering whether you really want to require CONFIG_XEN for the
> KVM case, though.
> 
> Wouldn't it be better to rename arch/x86/xen/enlighten_pvh.c to
> arch/x86/pvh.c and arch/x86/xen/xen-pvh.S to arch/x86/pvh-head.S,

Yes, sounds good.

> put both under CONFIG_PVH umbrella and select this from CONFIG_XEN_PVH
> and KVM_PVH (or what you like to call it)?

CONFIG_KVM_GUEST will be good enough.

> In the two moved source files you can make Xen/KVM-specific parts
> optional via their CONFIG_ options.
> 
> And you might want to add an own ELF note for the KVM case?

As long as it's compatible with Xen, it's not needed.  Only the startup
code changes between a KVM "PVH" kernel and a KVM "HVM" kernel.

Paolo