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Date: Fri, 1 Mar 2024 17:12:34 +0100
From: Borislav Petkov <bp@alien8.de>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Ard Biesheuvel <ardb+git@google.com>, linux-kernel@vger.kernel.org,
	Kevin Loughlin <kevinloughlin@google.com>,
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	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	Andy Lutomirski <luto@kernel.org>, Brian Gerst <brgerst@gmail.com>
Subject: Re: [PATCH v7 4/9] x86/startup_64: Simplify virtual switch on
 primary boot
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On Thu, Feb 29, 2024 at 11:36:01PM +0100, Ard Biesheuvel wrote:
> Because we enter with a 1:1 mapping, and so we can only switch to
> another set of page tables that also includes this 1:1 mapping. Once
> we are running from the kernel mapping, we can drop the 1:1 mapping
> but we still need it.
> 
> What we could do for robustness is reduce this 1:1 mapping to text +
> rodata, and make it read-only, but I'm not sure it's worth the churn.

Yeah, I was experimenting a bit with some shenanigans with those two
pagetables yesterday and arrived to a similar conclusion - there's no
point in trying to unify them.

Thx.

-- 
Regards/Gruss,
    Boris.

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