linux-kernel - Re: [PATCH v4 03/11] x86/startup_64: Simplify CR4 handling in startup code

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Message-ID: <20240219103259.GAZdMuWzLGRg6SR1n9@fat_crate.local>
Date: Mon, 19 Feb 2024 11:32:59 +0100
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.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>, Arnd Bergmann <arnd@...db.de>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Kees Cook <keescook@...omium.org>, Brian Gerst <brgerst@...il.com>,
	linux-arch@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH v4 03/11] x86/startup_64: Simplify CR4 handling in
 startup code

On Tue, Feb 13, 2024 at 01:41:47PM +0100, Ard Biesheuvel wrote:
> -#ifdef CONFIG_X86_5LEVEL
> -	testb	$1, __pgtable_l5_enabled(%rip)
> -	jz	1f
> -	orl	$X86_CR4_LA57, %ecx
> -1:
> +	orl	$X86_CR4_MCE, %edx
>  #endif
> +	movq	%cr4, %rcx
> +	andl	%edx, %ecx

Let's just state it explicitly:

	/* Even if ignored in long mode, set PSE uniformly on all logical CPUs. */

> +	btsl	$X86_CR4_PSE_BIT, %ecx
>  	movq	%rcx, %cr4

-- 
Regards/Gruss,
    Boris.

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