linux-kernel - Re: [RFC PATCH 14/21] KVM: x86/tdp_mmu: Invoke split_external_spt hook with exclusive mmu

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aCqtMgT3DA/AvC2s@yzhao56-desk.sh.intel.com>
Date: Mon, 19 May 2025 12:01:54 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "quic_eberman@...cinc.com"
	<quic_eberman@...cinc.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"david@...hat.com" <david@...hat.com>, "Li, Zhiquan1"
	<zhiquan1.li@...el.com>, "tabba@...gle.com" <tabba@...gle.com>,
	"vbabka@...e.cz" <vbabka@...e.cz>, "thomas.lendacky@....com"
	<thomas.lendacky@....com>, "michael.roth@....com" <michael.roth@....com>,
	"seanjc@...gle.com" <seanjc@...gle.com>, "Weiny, Ira" <ira.weiny@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>, "ackerleytng@...gle.com"
	<ackerleytng@...gle.com>, "Yamahata, Isaku" <isaku.yamahata@...el.com>,
	"binbin.wu@...ux.intel.com" <binbin.wu@...ux.intel.com>, "Peng, Chao P"
	<chao.p.peng@...el.com>, "Du, Fan" <fan.du@...el.com>, "Annapurve, Vishal"
	<vannapurve@...gle.com>, "jroedel@...e.de" <jroedel@...e.de>, "Miao, Jun"
	<jun.miao@...el.com>, "Shutemov, Kirill" <kirill.shutemov@...el.com>,
	"pgonda@...gle.com" <pgonda@...gle.com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [RFC PATCH 14/21] KVM: x86/tdp_mmu: Invoke split_external_spt
 hook with exclusive mmu_lock

On Sat, May 17, 2025 at 06:11:59AM +0800, Edgecombe, Rick P wrote:
> On Fri, 2025-05-16 at 17:17 +0800, Yan Zhao wrote:
> > > Shouldn't this BUG_ON be handled in the split_external_spt implementation? I
> > > don't think we need another one.
> > Ok. But kvm_x86_split_external_spt() is not for TDX only.
> > Is it good for KVM MMU core to rely on each implementation to trigger BUG_ON?
> 
> It effectively is for TDX only. At least for the foreseeable future. The naming
> basically means that people don't have to see "TDX" everywhere when they look in
> the MMU code.
Hmm, another reason to add the BUG_ON is to align it with remove_external_spte().
There's also a KVM_BUG_ON() following the remove_external_spte hook.

I interpret this as error handling in the KVM MMU core, which returns "void",
so issuing BUG_ON if ret != 0.