linux-kernel - Re: [PATCH v4 11/16] KVM: TDX: Add x86 ops for external spt cache

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Message-ID: <1e4711a1b68e9b5c268a463d5376463ae2978771.camel@intel.com>
Date: Tue, 20 Jan 2026 10:00:59 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "linux-coco@...ts.linux.dev"
	<linux-coco@...ts.linux.dev>, "Li, Xiaoyao" <xiaoyao.li@...el.com>, "Hansen,
 Dave" <dave.hansen@...el.com>, "Wu, Binbin" <binbin.wu@...el.com>,
	"kas@...nel.org" <kas@...nel.org>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "pbonzini@...hat.com" <pbonzini@...hat.com>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>, "tglx@...utronix.de"
	<tglx@...utronix.de>, "Annapurve, Vishal" <vannapurve@...gle.com>, "Gao,
 Chao" <chao.gao@...el.com>, "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	"bp@...en8.de" <bp@...en8.de>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v4 11/16] KVM: TDX: Add x86 ops for external spt cache

On Tue, 2026-01-20 at 17:18 +0800, Yan Zhao wrote:
> > When sp->spt is allocated via per-vCPU mmu_shadow_page_cache, it is
> > actually initialized to SHADOW_NONPRESENT_VALUE:
> > 
> >          vcpu->arch.mmu_shadow_page_cache.init_value =                    
> >                  SHADOW_NONPRESENT_VALUE;                                 
> > 
> > So the way sp->spt is allocated in tdp_mmu_alloc_sp_for_split() is
> > actually broken IMHO because entries in sp->spt is never initialized.
> The sp->spt allocated in tdp_mmu_alloc_sp_for_split() is initialized in
> tdp_mmu_split_huge_page()...

Oh right, we already have a huge SPTE to copy from in this case, so no
problem here, but seems the inconsistency is still there to me.