linux-kernel - Re: [RFC PATCH 03/21] x86/virt/tdx: Add SEAMCALL wrapper tdh_mem_page

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Message-ID: <55990bb0-9fbe-4b38-95db-bd257914b157@linux.intel.com>
Date: Fri, 25 Apr 2025 15:25:12 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
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, chao.p.peng@...el.com
Subject: Re: [RFC PATCH 03/21] x86/virt/tdx: Add SEAMCALL wrapper
 tdh_mem_page_demote()



On 4/25/2025 3:17 PM, Yan Zhao wrote:
> On Fri, Apr 25, 2025 at 03:12:32PM +0800, Binbin Wu wrote:
>>
>> On 4/24/2025 11:04 AM, Yan Zhao wrote:
>>> From: Xiaoyao Li <xiaoyao.li@...el.com>
>>>
>>> Add a wrapper tdh_mem_page_demote() to invoke SEAMCALL TDH_MEM_PAGE_DEMOTE
>>> to demote a huge leaf entry to a non-leaf entry in S-EPT. Currently, the
>>> TDX module only supports demotion of a 2M huge leaf entry. After a
>>> successful demotion, the old 2M huge leaf entry in S-EPT is replaced with a
>>> non-leaf entry, linking to the newly-added page table page. The newly
>>> linked page table page then contains 512 leaf entries, pointing to the 2M
>> 2M or 4K?
> The 512 leaf entries point to 2M guest private pages together,
If this, it should be 2M range, since it's not a huge page after demotion.
Also, the plural "pages" is confusing.

>   each pointing to
> 4K.
>
>>> guest private pages.