linux-kernel - Re: [PATCH v3 06/24] KVM: x86/mmu: Disallow page merging (huge page adjustment) for mirror root

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Message-ID: <aWlvF2rld0Nz3nRz@google.com>
Date: Thu, 15 Jan 2026 14:49:59 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Yan Zhao <yan.y.zhao@...el.com>
Cc: pbonzini@...hat.com, linux-kernel@...r.kernel.org, kvm@...r.kernel.org, 
	x86@...nel.org, rick.p.edgecombe@...el.com, dave.hansen@...el.com, 
	kas@...nel.org, tabba@...gle.com, ackerleytng@...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 06/24] KVM: x86/mmu: Disallow page merging (huge page
 adjustment) for mirror root

On Tue, Jan 06, 2026, Yan Zhao wrote:
> From: Rick P Edgecombe <rick.p.edgecombe@...el.com>
> 
> Disallow page merging (huge page adjustment) for the mirror root by
> utilizing disallowed_hugepage_adjust().

Why?  What is this actually doing?  The below explains "how" but I'm baffled as
to the purpose.  I'm guessing there are hints in the surrounding patches, but I
haven't read them in depth, and shouldn't need to in order to understand the
primary reason behind a change.