linux-kernel - Re: [PATCH v3 01/24] x86/tdx: Enhance tdh_mem_page

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Message-ID: <CAGtprH_4MyZxQ9y=MB7cR-Kzots2=H5Cp4hf_GnH9-CTw+gO1Q@mail.gmail.com>
Date: Fri, 9 Jan 2026 08:21:11 -0800
From: Vishal Annapurve <vannapurve@...gle.com>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Ackerley Tng <ackerleytng@...gle.com>, Yan Zhao <yan.y.zhao@...el.com>, pbonzini@...hat.com, 
	seanjc@...gle.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	x86@...nel.org, rick.p.edgecombe@...el.com, kas@...nel.org, tabba@...gle.com, 
	michael.roth@....com, david@...nel.org, sagis@...gle.com, vbabka@...e.cz, 
	thomas.lendacky@....com, nik.borisov@...e.com, pgonda@...gle.com, 
	fan.du@...el.com, jun.miao@...el.com, francescolavra.fl@...il.com, 
	jgross@...e.com, ira.weiny@...el.com, isaku.yamahata@...el.com, 
	xiaoyao.li@...el.com, kai.huang@...el.com, binbin.wu@...ux.intel.com, 
	chao.p.peng@...el.com, chao.gao@...el.com
Subject: Re: [PATCH v3 01/24] x86/tdx: Enhance tdh_mem_page_aug() to support
 huge pages

On Thu, Jan 8, 2026 at 11:24 AM Dave Hansen <dave.hansen@...el.com> wrote:
>
> On 1/8/26 11:05, Ackerley Tng wrote:
> ...
> >> All of those properties are important and they're *GONE* if you use a
> >> pfn. It's even worse if you use a raw physical address.
> >
> > We were thinking through what it would take to have TDs use VM_PFNMAP
> > memory, where the memory may not actually have associated struct
> > pages. Without further work, having struct pages in the TDX interface
> > would kind of lock out those sources of memory. Is TDX open to using
> > non-kernel managed memory?
>
> I was afraid someone was going to bring that up. I'm not open to such a
> beast today. I'd certainly look at the patches, but it would be a hard
> sell and it would need an awfully strong justification.

Yeah, I will punt this discussion to later when we have something
working on the guest_memfd side. I expect that discussion will carry a
strong justification, backed by all the complexity in guest_memfd.

>
> > For type safety, would phyrs help? [1] Perhaps starting with pfn/paddrs
> > + nr_pages would allow transitioning to phyrs later. Using pages would
> > be okay for now, but I would rather not use folios.
>
> I don't have any first-hand experience with phyrs. It seems interesting,
> but might be unwieldy to use in practice, kinda how the proposed code
> got messy when folios got thrown in.