linux-kernel - Re: [PATCH 3/4] x86/kexec(): Reset TDX private memory on platforms with TDX erratum

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Message-ID: <86ad296c-7af0-49ba-a22b-9bcaf355311e@intel.com>
Date: Mon, 5 Feb 2024 14:44:51 +0800
From: "Huang, Kai" <kai.huang@...el.com>
To: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "Gao, Chao" <chao.gao@...el.com>, "Hansen, Dave" <dave.hansen@...el.com>,
	"luto@...nel.org" <luto@...nel.org>, "bp@...en8.de" <bp@...en8.de>,
	"x86@...nel.org" <x86@...nel.org>, "peterz@...radead.org"
	<peterz@...radead.org>, "hpa@...or.com" <hpa@...or.com>, "mingo@...hat.com"
	<mingo@...hat.com>, "kirill.shutemov@...ux.intel.com"
	<kirill.shutemov@...ux.intel.com>, "tglx@...utronix.de" <tglx@...utronix.de>,
	"bhe@...hat.com" <bhe@...hat.com>, "thomas.lendacky@....com"
	<thomas.lendacky@....com>, "nik.borisov@...e.com" <nik.borisov@...e.com>,
	"pbonzini@...hat.com" <pbonzini@...hat.com>
Subject: Re: [PATCH 3/4] x86/kexec(): Reset TDX private memory on platforms
 with TDX erratum



On 2/02/2024 8:54 am, Edgecombe, Rick P wrote:
> On Wed, 2024-01-31 at 11:31 +0000, Huang, Kai wrote:
>> Note kexec() can happen at anytime, including when TDX module is
>> being
>> initialized.  Register TDX reboot notifier callback to stop further
>> TDX
>> module initialization.  If there's any ongoing module initialization,
>> wait until it finishes.  This makes sure the TDX module status is
>> stable
>> after the reboot notifier callback, and the later kexec() code can
>> read
>> module status to decide whether PAMTs are stable and available.
> 
> I don't see how this works with the crash kernel flavor of kexec. Did
> you look at that scenario?
> 
> 
Hmm right this doesn't work for crash kexec.  Thanks for pointing out.

We need a way that doesn't depend on the reboot notifier.  Previously we 
used a variable to indicate the point where it's possible to have any 
TDX private pages.  I'll switch back to use that.