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

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Message-ID: <aAn7K9O8GKAvU/nz@yzhao56-desk.sh.intel.com>
Date: Thu, 24 Apr 2025 16:49:47 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: "Kirill A. Shutemov" <kirill@...temov.name>
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 10:55:53AM +0300, Kirill A. Shutemov wrote:
> 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/
Right. Thanks!