linux-kernel - Re: [RFC PATCH 08/21] KVM: TDX: Increase/decrease folio ref for huge pages

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Message-ID: <4c70424ab8bc076142e5f6e8423f207539602ff1.camel@intel.com>
Date: Fri, 11 Jul 2025 16:14:22 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.com>
CC: "quic_eberman@...cinc.com" <quic_eberman@...cinc.com>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "Du, Fan" <fan.du@...el.com>, "Hansen, Dave"
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	"Peng, Chao P" <chao.p.peng@...el.com>, "pbonzini@...hat.com"
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	"jroedel@...e.de" <jroedel@...e.de>, "Miao, Jun" <jun.miao@...el.com>,
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	<pgonda@...gle.com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC PATCH 08/21] KVM: TDX: Increase/decrease folio ref for huge
 pages

On Fri, 2025-07-11 at 13:12 +0800, Yan Zhao wrote:
> > Yan, is that your recollection? I guess the other points were that although
> > TDX
> I'm ok if KVM_BUG_ON() is considered loud enough to warn about the rare
> potential corruption, thereby making TDX less special.
> 
> > doesn't need it today, for long term, userspace ABI around invalidations
> > should
> > support failure. But the actual gmem/kvm interface for this can be figured
> > out
> Could we elaborate what're included in userspace ABI around invalidations?

Let's see what Ackerley says.

> 
> I'm a bit confused as I think the userspace ABI today supports failure
> already.
> 
> Currently, the unmap API between gmem and KVM does not support failure.

Great. I'm just trying to summarize the internal conversations. I think the
point was for a future looking user ABI, supporting failure is important. But we
don't need the KVM/gmem interface figured out yet.

> 
> In the future, we hope gmem can check if KVM allows a page to be unmapped
> before
> triggering the actual unmap.