linux-kernel - Re: [PATCH v3 2/2] KVM: X86: Introduce KVM_HC_PAGE_ENC

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Date:   Tue, 4 May 2021 20:33:49 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        srutherford@...gle.com, joro@...tes.org, brijesh.singh@....com,
        thomas.lendacky@....com, ashish.kalra@....com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        x86@...nel.org
Subject: Re: [PATCH v3 2/2] KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS
 hypercall

On Tue, May 04, 2021, Paolo Bonzini wrote:
> On 04/05/21 19:09, Sean Christopherson wrote:
> > On Sat, May 01, 2021, Paolo Bonzini wrote:
> > > - make it completely independent from migration, i.e. it's just a facet of
> > > MSR_KVM_PAGE_ENC_STATUS saying whether the bitmap is up-to-date.  It would
> > > use CPUID bit as the encryption status bitmap and have no code at all in KVM
> > > (userspace needs to set up the filter and implement everything).
> > 
> > If the bit is purely a "page encryption status is up-to-date", what about
> > overloading KVM_HC_PAGE_ENC_STATUS to handle that status update as well?   That
> > would eliminate my biggest complaint about having what is effectively a single
> > paravirt feature split into two separate, but intertwined chunks of ABI.
> 
> It's true that they are intertwined, but I dislike not having a way to read
> the current state.

>From the guest?