linux-kernel - Re: [PATCH v5 3/7] x86/mm: Define PTRS_PER_P4D in terms of pgdir

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Message-ID: <nlkjrtpuohrsg3u2gqhia7ns7ogrik7ztmks5q5bdhn3y4kfhi@k7yxsyc7j4fe>
Date: Tue, 20 May 2025 14:08:15 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org, 
	Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>, 
	Linus Torvalds <torvalds@...ux-foundation.org>, Brian Gerst <brgerst@...il.com>, Borislav Petkov <bp@...en8.de>
Subject: Re: [PATCH v5 3/7] x86/mm: Define PTRS_PER_P4D in terms of
 pgdir_shift()

On Tue, May 20, 2025 at 12:41:42PM +0200, Ard Biesheuvel wrote:
> @@ -61,7 +59,7 @@ extern unsigned int ptrs_per_p4d;
>   */
>  #define P4D_SHIFT		39
>  #define MAX_PTRS_PER_P4D	512
> -#define PTRS_PER_P4D		ptrs_per_p4d
> +#define PTRS_PER_P4D		(pgdir_shift() & 1 ?: MAX_PTRS_PER_P4D)

"& 1" is a hack and at least deserves a comment.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov