linux-kernel - Re: [RFC PATCH v5 032/104] KVM: x86/mmu: introduce config for PRIVATE KVM MMU

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Date:   Thu, 31 Mar 2022 18:51:30 -0700
From:   Isaku Yamahata <isaku.yamahata@...il.com>
To:     Kai Huang <kai.huang@...el.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 032/104] KVM: x86/mmu: introduce config for
 PRIVATE KVM MMU

On Fri, Apr 01, 2022 at 12:23:28AM +1300,
Kai Huang <kai.huang@...el.com> wrote:

> On Fri, 2022-03-04 at 11:48 -0800, isaku.yamahata@...el.com wrote:
> > From: Isaku Yamahata <isaku.yamahata@...el.com>
> > 
> > To Keep the case of non TDX intact, introduce a new config option for
> > private KVM MMU support.  At the moment, this is synonym for
> > CONFIG_INTEL_TDX_HOST && CONFIG_KVM_INTEL.  The new flag make it clear
> > that the config is only for x86 KVM MMU.
> > 
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > ---
> >  arch/x86/kvm/Kconfig | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
> > index 2b1548da00eb..2db590845927 100644
> > --- a/arch/x86/kvm/Kconfig
> > +++ b/arch/x86/kvm/Kconfig
> > @@ -136,4 +136,8 @@ config KVM_MMU_AUDIT
> >  config KVM_EXTERNAL_WRITE_TRACKING
> >  	bool
> >  
> > +config KVM_MMU_PRIVATE
> > +	def_bool y
> > +	depends on INTEL_TDX_HOST && KVM_INTEL
> > +
> >  endif # VIRTUALIZATION
> 
> I am really not sure why need this.  Roughly looking at MMU related patches this
> new config option is hardly used.  You have many code changes related to
> handling private/shared but they are not under this config option.

I don't want to use CONFIG_INTEL_TDX_HOST in KVM MMU code.  I think the change
to KVM MMU should be a sort of independent from TDX.  But it seems failed based
on your feedback.
-- 
Isaku Yamahata <isaku.yamahata@...il.com>