linux-kernel - Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

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Message-ID: <CAGtprH_1nMC_z+ut3H6Hjjjb9J=sg=h-H10L9PVK+x=Vw2SM0w@mail.gmail.com>
Date: Wed, 25 Jun 2025 06:47:40 -0700
From: Vishal Annapurve <vannapurve@...gle.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
Cc: "Zhao, Yan Y" <yan.y.zhao@...el.com>, 
	"quic_eberman@...cinc.com" <quic_eberman@...cinc.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, 
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	"Hansen, Dave" <dave.hansen@...el.com>, "david@...hat.com" <david@...hat.com>, 
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Subject: Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

On Tue, Jun 24, 2025 at 11:36 AM Edgecombe, Rick P
<rick.p.edgecombe@...el.com> wrote:
> ...
> For leaving the option open to promote the GFNs in the future, a GHCI interface
> or similar could be defined for the guest to say "I don't care about page size
> anymore for this gfn". So it won't close it off forever.
>

I think it's in the host's interest to get the pages mapped at large
page granularity whenever possible. Even if guest doesn't buy-in into
the "future" GHCI interface, there should be some ABI between TDX
module and host VMM to allow promotion probably as soon as all the
ranges within a hugepage get accepted but are still mapped at 4K
granularity.