linux-kernel - Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is RUNNABLE

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Message-ID: <67419b2b9addefa0b728bf30099f55edf58964ed.camel@intel.com>
Date: Wed, 2 Jul 2025 15:26:54 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "Zhao, Yan Y" <yan.y.zhao@...el.com>
CC: "Du, Fan" <fan.du@...el.com>, "Li, Xiaoyao" <xiaoyao.li@...el.com>,
	"Huang, Kai" <kai.huang@...el.com>, "Shutemov, Kirill"
	<kirill.shutemov@...el.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"david@...hat.com" <david@...hat.com>, "thomas.lendacky@....com"
	<thomas.lendacky@....com>, "vbabka@...e.cz" <vbabka@...e.cz>, "Li, Zhiquan1"
	<zhiquan1.li@...el.com>, "quic_eberman@...cinc.com"
	<quic_eberman@...cinc.com>, "michael.roth@....com" <michael.roth@....com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Weiny, Ira" <ira.weiny@...el.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "Peng, Chao P"
	<chao.p.peng@...el.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>,
	"ackerleytng@...gle.com" <ackerleytng@...gle.com>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "Annapurve, Vishal" <vannapurve@...gle.com>,
	"tabba@...gle.com" <tabba@...gle.com>, "jroedel@...e.de" <jroedel@...e.de>,
	"Miao, Jun" <jun.miao@...el.com>, "pgonda@...gle.com" <pgonda@...gle.com>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC PATCH 09/21] KVM: TDX: Enable 2MB mapping size after TD is
 RUNNABLE

On Wed, 2025-07-02 at 09:07 +0800, Yan Zhao wrote:
> > I don't think because some code might race in the future is a good reason to
> > take the write lock.
> 
> I still prefer to hold write mmu_lock right now.
> 
> Otherwise, we at least need to convert disallow_lpage to atomic variable and
> updating it via an atomic way, e.g. cmpxchg. 
> 
> struct kvm_lpage_info {
>         int disallow_lpage;
> };

This seems like a valid reason. I wanted to make sure there was some reason,
besides it feels safer.