linux-kernel - Re: [PATCH v5 2/7] x86/mm: Use a single cache hot per-CPU variable to record pgdir

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Message-ID: <20250520183540.GQaCzLfHsGoWtt_6ZV@fat_crate.local>
Date: Tue, 20 May 2025 20:35:40 +0200
From: Borislav Petkov <bp@...en8.de>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Ard Biesheuvel <ardb@...nel.org>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Ingo Molnar <mingo@...nel.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH v5 2/7] x86/mm: Use a single cache hot per-CPU variable
 to record pgdir_shift

On Tue, May 20, 2025 at 11:28:28AM -0700, Linus Torvalds wrote:
> What happens if pgtable_l5_enabled() is made to use  __raw_cpu_read()?
> With a compiler that is new enough to support USE_X86_SEG_SUPPORT?

Before we go play with this more, I see the same thing with gcc-13 and gcc-14
on debian.

Those should be fairly new, I'd think...

-- 
Regards/Gruss,
    Boris.

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