linux-kernel - Re: [PATCHv3 3/4] x86/64/kexec: Map original relocate_kernel() in init_transition

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Message-ID: <4f9cd14415f1c01c937f6b3bdd56ba0243d47f94.camel@intel.com>
Date: Tue, 20 Aug 2024 11:52:29 +0000
From: "Huang, Kai" <kai.huang@...el.com>
To: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
CC: "ardb@...nel.org" <ardb@...nel.org>, "luto@...nel.org" <luto@...nel.org>,
	"tzimmermann@...e.de" <tzimmermann@...e.de>, "dave.hansen@...ux.intel.com"
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	<thomas.lendacky@....com>, "akpm@...ux-foundation.org"
	<akpm@...ux-foundation.org>, "linux-kernel@...r.kernel.org"
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	"bp@...en8.de" <bp@...en8.de>, "rafael@...nel.org" <rafael@...nel.org>,
	"Huang, Ying" <ying.huang@...el.com>, "linux-acpi@...r.kernel.org"
	<linux-acpi@...r.kernel.org>, "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCHv3 3/4] x86/64/kexec: Map original relocate_kernel() in
 init_transition_pgtable()

On Tue, 2024-08-20 at 14:14 +0300, kirill.shutemov@...ux.intel.com wrote:
> On Tue, Aug 20, 2024 at 11:06:34AM +0000, Huang, Kai wrote:
> > At later time:
> > 
> >         call    swap_pages                                                   
> >         movq    $virtual_mapped, %rax  	<---- (1)                            
> >         pushq   %rax
> >         ANNOTATE_UNRET_SAFE
> >         ret  				<---- (2)
> > 
> > (1) will load the VA which has __START_KERNEL_map to %rax, and after (2) the
> > kernel will run at VA of the original relocate_kernel() which maps to the PA
> > of the original relcoate_kernel().  But I think the memory page of the
> > original relocate_kernel() won't get corrupted after returning from the second
> > kernel, so should be safe to use?
> 
> Yes.
> 

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