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From:   Fuad Tabba <tabba@google.com>
Date:   Wed, 19 Oct 2022 19:32:21 +0100
Message-ID: <CA+EHjTzR6DwU950gud1opEGCNqCfiEvA4-JFtyJ0NBgTD-uHNg@mail.gmail.com>
Subject: Re: [PATCH v8 5/8] KVM: Register/unregister the guest private memory regions
To:     Sean Christopherson <seanjc@google.com>
Cc:     Chao Peng <chao.p.peng@linux.intel.com>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
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        Jim Mattson <jmattson@google.com>,
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On Wed, Oct 19, 2022 at 5:09 PM Sean Christopherson <seanjc@google.com> wrote:
>
> On Wed, Oct 19, 2022, Fuad Tabba wrote:
> > > > > This sounds good. Thank you.
> > > >
> > > > I like the idea of a separate Kconfig, e.g. CONFIG_KVM_GENERIC_PRIVATE_MEM or
> > > > something.  I highly doubt there will be any non-x86 users for multiple years,
> > > > if ever, but it would allow testing the private memory stuff on ARM (and any other
> > > > non-x86 arch) without needing full pKVM support and with only minor KVM
> > > > modifications, e.g. the x86 support[*] to test UPM without TDX is shaping up to be
> > > > trivial.
> > >
> > > CONFIG_KVM_GENERIC_PRIVATE_MEM looks good to me.
> >
> > That sounds good to me, and just keeping the xarray isn't really an
> > issue for pKVM.
>
> The xarray won't exist for pKVM if the #ifdefs in this patch are changed from
> CONFIG_HAVE_KVM_PRIVATE_MEM => CONFIG_KVM_GENERIC_PRIVATE_MEM.
>
> > We could end up using it instead of some of the other
> > structures we use for tracking.
>
> I don't think pKVM should hijack the xarray for other purposes.  At best, it will
> be confusing, at worst we'll end up with a mess if ARM ever supports the "generic"
> implementation.

Definitely wasn't referring to hijacking it for other purposes, which
is the main reason I wanted to clarify the documentation and the
naming of private_fd. Anyway, I'm glad to see that we're in agreement.
Once I've tightened the screws, I'll share the pKVM port as an RFC as
well.

Cheers,
/fuad