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

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Message-ID: <f001881a152772b623ff9d3bb6ca5b2f72034db9.camel@intel.com>
Date: Thu, 12 Jun 2025 23:39:00 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "seanjc@...gle.com" <seanjc@...gle.com>, "Huang, Kai"
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 P" <chao.p.peng@...el.com>, "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
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Subject: Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is
 RUNNABLE

On Wed, 2025-06-11 at 07:42 -0700, Sean Christopherson wrote:
> If there's a *legitimate* use case where the guest wants to ACCEPT a subset of
> memory, then there should be an explicit TDCALL to request that the unwanted
> regions of memory be unmapped.  Smushing everything into implicit behavior has
> obvioulsy created a giant mess.

Hi, still digging on if there is any possible use.

I think this may need a guest opt-in, so the guest can say it can handle errors
for both smaller and larger page size matches. So it may not matter if there is
a rare usage or not. If KVM finds the guest opts-in (how to do that TBD), it can
start mapping at the host level. If KVM doesn't see the opt-in, the guest gets
4k pages.