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

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Message-ID: <305c16d7-803e-42fa-b540-025e8571452b@intel.com>
Date: Thu, 8 Jan 2026 11:24:29 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Ackerley Tng <ackerleytng@...gle.com>, Yan Zhao <yan.y.zhao@...el.com>
Cc: 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,
 vannapurve@...gle.com, 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 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.

> 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.