linux-kernel - Re: [PATCH 0/3] Resolve problems with kexec identity mapping

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Message-ID: <20240709103139.GBZo0Ri_ppOUNnKd_2@fat_crate.local>
Date: Tue, 9 Jul 2024 12:31:39 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Steve Wahl <steve.wahl@....com>, Ashish Kalra <ashish.kalra@....com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Pavin Joseph <me@...injoseph.com>,
	Eric Hagberg <ehagberg@...il.com>,
	Simon Horman <horms@...ge.net.au>,
	Eric Biederman <ebiederm@...ssion.com>,
	Dave Young <dyoung@...hat.com>, Sarah Brofeldt <srhb@....dk>,
	Russ Anderson <rja@....com>, Dimitri Sivanich <sivanich@....com>,
	Hou Wenlong <houwenlong.hwl@...group.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Baoquan He <bhe@...hat.com>, Yuntao Wang <ytcoode@...il.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>, Joerg Roedel <jroedel@...e.de>,
	Michael Roth <michael.roth@....com>
Subject: Re: [PATCH 0/3] Resolve problems with kexec identity mapping

On Mon, Jul 08, 2024 at 11:05:29PM +0200, Ard Biesheuvel wrote:
> The EFI config table array can grow and shrink at boot time, which is
> why it is a separate allocation, as this allows it to be realloc()'ed.
> This means any bootloader that intends to map the primary EFI table
> should also map the EFI config table array, which may be elsewhere
> entirely.

Yap, that rings a bell from a past thread.

> So regardless of how we fix any SEV-guest specific issues, we should
> ensure that kexec infrastructure creates the mappings of the EFI
> system table and the EFI config table array upfront.

Because code in the kernel relies on the presence of those so those should be
mapped automatically and unconditionally?

Or?

As long as we put that somewhere as the thing we do by default, sure, I'm
game.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette