linux-kernel - Re: [PATCH 10/16] KVM: x86/tdp_mmu: Support TDX private mapping for TDP MMU

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Message-ID: <CABgObfYCnC2qoMHmKx7QK=pEoARfcGw=F-epXYT4z6uoJeH_-w@mail.gmail.com>
Date: Wed, 29 May 2024 09:25:46 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "isaku.yamahata@...il.com" <isaku.yamahata@...il.com>, "seanjc@...gle.com" <seanjc@...gle.com>, 
	"Huang, Kai" <kai.huang@...el.com>, "sagis@...gle.com" <sagis@...gle.com>, 
	"isaku.yamahata@...ux.intel.com" <isaku.yamahata@...ux.intel.com>, "Zhao, Yan Y" <yan.y.zhao@...el.com>, 
	"Aktas, Erdem" <erdemaktas@...gle.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "dmatlack@...gle.com" <dmatlack@...gle.com>, 
	"Yamahata, Isaku" <isaku.yamahata@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH 10/16] KVM: x86/tdp_mmu: Support TDX private mapping for
 TDP MMU

On Wed, May 29, 2024 at 4:14 AM Edgecombe, Rick P
<rick.p.edgecombe@...el.com> wrote:
>
> On Tue, 2024-05-28 at 19:47 +0200, Paolo Bonzini wrote:
> > On Tue, May 28, 2024 at 6:27 PM Edgecombe, Rick P
> > <rick.p.edgecombe@...el.com> wrote:
> > > > I don't see benefit of x86_ops.max_gfn() compared to kvm->arch.max_gfn.
> > > > But I don't have strong preference. Either way will work.
> > >
> > > The non-TDX VM's won't need per-VM data, right? So it's just unneeded extra
> > > state per-vm.
> >
> > It's just a cached value like there are many in the MMU. It's easier
> > for me to read code without the mental overhead of a function call.
>
> Ok. Since this has (optimization) utility beyond TDX, maybe it's worth splitting
> it off as a separate patch? I think maybe we'll pursue this path unless there is
> objection.

Yes, absolutely.

Paolo