linux-kernel - Re: [PATCH 2/2] KVM: TDX: Do not clear poisoned pages

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Message-ID: <83e34b6cfa1d25857a085db835a43459a1d6a97c.camel@intel.com>
Date: Wed, 18 Jun 2025 23:09:48 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "Luck, Tony" <tony.luck@...el.com>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "Hunter, Adrian" <adrian.hunter@...el.com>,
	"seanjc@...gle.com" <seanjc@...gle.com>
CC: "kvm@...r.kernel.org" <kvm@...r.kernel.org>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "Zhao, Yan Y" <yan.y.zhao@...el.com>,
	"dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
	"tony.lindgren@...ux.intel.com" <tony.lindgren@...ux.intel.com>,
	"mingo@...hat.com" <mingo@...hat.com>, "Chatre, Reinette"
	<reinette.chatre@...el.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "binbin.wu@...ux.intel.com"
	<binbin.wu@...ux.intel.com>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"Yamahata, Isaku" <isaku.yamahata@...el.com>, "linux-edac@...r.kernel.org"
	<linux-edac@...r.kernel.org>, "hpa@...or.com" <hpa@...or.com>, "Annapurve,
 Vishal" <vannapurve@...gle.com>, "Edgecombe, Rick P"
	<rick.p.edgecombe@...el.com>, "bp@...en8.de" <bp@...en8.de>, "Gao, Chao"
	<chao.gao@...el.com>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 2/2] KVM: TDX: Do not clear poisoned pages

On Wed, 2025-06-18 at 15:08 +0300, Hunter, Adrian wrote:
> Skip clearing a private page if it is marked as poisoned.
> 
> The machine check architecture may have the capability to recover from
							 ^
"to recover" -> "to allow the kernel to recover"?

> memory corruption in SEAM non-root (i.e. TDX VM guest) mode.  In that
> case the page is marked as poisoned, and the TDX Module puts the TDX VM

"marked as poisoned" -> "marked as poisoned in the kernel"?  Since next half
of this sentence immediately talks about TDX module behaviour.

> into a FATAL error state where the only operation permitted is to tear it
> down.
> 
> During tear down, reclaimed pages are cleared which, in some cases,  helps
								      ^

Double writespace in middle of sentence.

> to avoid integrity violation or TD bit mismatch detection when later being
> read using a shared HKID.
> 
> However a poisoned page will never be allocated again, so clearing is not
> necessary, and in any case poisoned pages should not be touched.
> 
> Note that while it is possible that memory corruption arises from integrity
> violation which could be cleared by MOVDIR64B, that is not necessarily the
> cause of the machine check.
> 
> Suggested-by: Kai Huang <kai.huang@...el.com>
> Fixes: 8d032b683c299 ("KVM: TDX: create/destroy VM structure")
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>

With comments from Xiaoyao/Dave fixed,

Reviewed-by: Kai Huang <kai.huang@...el.com>