linux-kernel - Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

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Message-ID: <CALu+AoRqNmsWXi+HXYNYTY=pXJ3sLTLKyXNeJz9EoxEsHzFdQA@mail.gmail.com>
Date: Wed, 5 Jun 2024 10:53:44 +0800
From: Dave Young <dyoung@...hat.com>
To: Borislav Petkov <bp@...en8.de>
Cc: Mike Rapoport <rppt@...nel.org>, "Kalra, Ashish" <ashish.kalra@....com>, tglx@...utronix.de, 
	mingo@...hat.com, dave.hansen@...ux.intel.com, x86@...nel.org, 
	rafael@...nel.org, hpa@...or.com, peterz@...radead.org, 
	adrian.hunter@...el.com, sathyanarayanan.kuppuswamy@...ux.intel.com, 
	jun.nakajima@...el.com, rick.p.edgecombe@...el.com, thomas.lendacky@....com, 
	michael.roth@....com, seanjc@...gle.com, kai.huang@...el.com, bhe@...hat.com, 
	kirill.shutemov@...ux.intel.com, bdas@...hat.com, vkuznets@...hat.com, 
	dionnaglaze@...gle.com, anisinha@...hat.com, jroedel@...e.de, ardb@...nel.org, 
	kexec@...ts.infradead.org, linux-coco@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 1/3] efi/x86: Fix EFI memory map corruption with kexec

On Wed, 5 Jun 2024 at 02:03, Borislav Petkov <bp@...en8.de> wrote:
>
> On Tue, Jun 04, 2024 at 07:09:56PM +0800, Dave Young wrote:
> > Anyway there is not such a helper for all cases.
>
> But maybe there should be...
>
> This is not the first case where the need arises to be able to say:
>
>         if (am I a kexeced kernel)
>
> in code.
>
> Perhaps we should have a global var kexeced or so which gets incremented
> on each kexec-ed kernel, somewhere in very early boot of the kexec-ed
> kernel we do
>
>         kexeced++;
>
> and then other code can query it and know whether this is a kexec-ed
> kernel and how many times it got kexec-ed...

It's something good to have but not must for the time being,  also no
idea how to save the status across boot, for EFI boot case probably a
EFI var can be used, but how can it be cleared in case of physical
boot.    Otherwise probably injecting some kernel parameters, anyway
this needs more thinking.

>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette
>