linux-kernel - Re: [PATCH v7 9/9] x86/startup_64: Drop global variables keeping track of LA57 state

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Message-ID: <20240302182224.GDZeNuYD6vGvEP-J45@fat_crate.local>
Date: Sat, 2 Mar 2024 19:22:24 +0100
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: linux-kernel@...r.kernel.org, Kevin Loughlin <kevinloughlin@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Dionna Glaze <dionnaglaze@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>, Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH v7 9/9] x86/startup_64: Drop global variables keeping
 track of LA57 state

On Sat, Mar 02, 2024 at 04:32:19PM +0100, Ard Biesheuvel wrote:
> That is not the issue here. The issue is that cpu_feature_enabled()
> will produce the wrong value if you call it too early.

Looks like I didn't express myself too clearly: the early version of
early_pgtable_l5_enabled() should use a simple variable like now - not
cpu_feature_enabled().

And regardless, cpu_feature_enabled() should work even before
alternatives have run because we do dynamic testing in that case... and
so on and so on.

BUT(!), let's put a pin in this and let me first have an indepth look
after the merge window so that I can poke at the details and produce
a concrete diff which we can talk about.

Thx.

-- 
Regards/Gruss,
    Boris.

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