linux-kernel - Re: [RFC PATCH 04/21] KVM: TDX: Enforce 4KB mapping level during TD build Time

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Message-ID: <g3htfhtzg23aynnmv4pqwothiub5ojewvm3xgoyfn7rpfwru5j@fdnrdiz3to7a>
Date: Thu, 24 Apr 2025 10:55:53 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: 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, 
	dave.hansen@...el.com, kirill.shutemov@...el.com, tabba@...gle.com, 
	ackerleytng@...gle.com, quic_eberman@...cinc.com, michael.roth@....com, david@...hat.com, 
	vannapurve@...gle.com, vbabka@...e.cz, jroedel@...e.de, thomas.lendacky@....com, 
	pgonda@...gle.com, zhiquan1.li@...el.com, fan.du@...el.com, jun.miao@...el.com, 
	ira.weiny@...el.com, isaku.yamahata@...el.com, xiaoyao.li@...el.com, 
	binbin.wu@...ux.intel.com, chao.p.peng@...el.com
Subject: Re: [RFC PATCH 04/21] KVM: TDX: Enforce 4KB mapping level during TD
 build Time

On Thu, Apr 24, 2025 at 11:05:00AM +0800, Yan Zhao wrote:
> During the TD build phase (i.e., before the TD becomes RUNNABLE), enforce a
> 4KB mapping level both in the S-EPT managed by the TDX module and the
> mirror page table managed by KVM.
> 
> During this phase, TD's memory is added via tdh_mem_page_add(), which only
> accepts 4KB granularity. Therefore, return PG_LEVEL_4K in TDX's
> .private_max_mapping_level hook to ensure KVM maps at the 4KB level in the
> mirror page table. Meanwhile, iterate over each 4KB page of a large gmem
> backend page in tdx_gmem_post_populate() and invoke tdh_mem_page_add() to
> map at the 4KB level in the S-EPT.
> 
> Still allow huge pages in gmem backend during TD build time. Based on [1],
> which gmem series allows 2MB TPH and non-in-place conversion, pass in

s/TPH/THP/

-- 
  Kiryl Shutsemau / Kirill A. Shutemov