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

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Date:   Fri, 01 Apr 2022 15:13:27 +1300
From:   Kai Huang <kai.huang@...el.com>
To:     Isaku Yamahata <isaku.yamahata@...il.com>
Cc:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, 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 Thu, 2022-03-31 at 18:51 -0700, Isaku Yamahata wrote:
> 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.

Why do you need to use any config?  As I said majority of your changes to MMU
are not under any config.  But I'll leave this to maintainer/reviewers. 

-- 
Thanks,
-Kai