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

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Message-ID: <hxw67ecixuf5mkj3ucwhsobvd6dyjhwjo32fu4jiwoxgrgk7rd@dklvwlnrewil>
Date: Tue, 20 Aug 2024 14:14:47 +0300
From: "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>
To: "Huang, Kai" <kai.huang@...el.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" <dave.hansen@...ux.intel.com>, "thomas.lendacky@....com" <thomas.lendacky@....com>, 
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"mingo@...hat.com" <mingo@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>, 
	"tglx@...utronix.de" <tglx@...utronix.de>, "bhe@...hat.com" <bhe@...hat.com>, 
	"hpa@...or.com" <hpa@...or.com>, "peterz@...radead.org" <peterz@...radead.org>, 
	"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, 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.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov