linux-kernel - Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in relocate

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Date: Thu, 21 Mar 2024 09:48:28 +1300
From: "Huang, Kai" <kai.huang@...el.com>
To: Tom Lendacky <thomas.lendacky@....com>, "Kirill A. Shutemov"
	<kirill.shutemov@...ux.intel.com>
CC: <linux-kernel@...r.kernel.org>, <x86@...nel.org>, <dave.hansen@...el.com>,
	<bp@...en8.de>, <tglx@...utronix.de>, <mingo@...hat.com>, <hpa@...or.com>,
	<luto@...nel.org>, <peterz@...radead.org>, <rick.p.edgecombe@...el.com>,
	<ashish.kalra@....com>, <chao.gao@...el.com>, <bhe@...hat.com>,
	<nik.borisov@...e.com>, <pbonzini@...hat.com>, <seanjc@...gle.com>
Subject: Re: [PATCH v2 2/5] x86/kexec: do unconditional WBINVD in
 relocate_kernel()


>> Hi Tom,
>>
>> I am not aware of kexec() support status for SEV-ES/SEV-SNP guests. 
>> Does patch 1 break them?
> 
> SNP guests can kexec with some patches that are currently in process 
> around shared to private memory conversions. ES guests can only kexec 
> with a single vCPU. There was a recent patch series to add support for 
> multiple vCPUs.
> 
> Patch #1 doesn't break either ES or SNP because we still have an IDT and 
> traditional kernel addressing in place, so the #VC can be handled.

How about plain SEV guest?

> 
> Whereas patch #2 has switched to identity mapping and removed the IDT, 
> so a #VC causes a triple fault.

That makes sense.  Thanks.

Hi Kirill,

Does TDX guest have similar behaviour -- that WBINVD in stop_this_cpu() 
can be handled although it causes #VE, while WBINVD in relocate_kernel() 
will just triple fault the guest?