linux-kernel - Re: [PATCH v3 02/19] x86/boot: Move mem_encrypt= parsing to the decompressor

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Message-ID: <20240131083511.GIZboGP8jPIrUZA8DF@fat_crate.local>
Date: Wed, 31 Jan 2024 09:35:11 +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 v3 02/19] x86/boot: Move mem_encrypt= parsing to the
 decompressor

On Mon, Jan 29, 2024 at 07:05:05PM +0100, Ard Biesheuvel wrote:
> +/*
> + * Set the memory encryption xloadflag based on the mem_encrypt= command line
> + * parameter, if provided. If not, the consumer of the flag decides what the
> + * default behavior should be.
> + */
> +static void set_mem_encrypt_flag(struct setup_header *hdr)

parse_mem_encrypt

> +{
> +	hdr->xloadflags &= ~(XLF_MEM_ENCRYPTION | XLF_MEM_ENCRYPTION_ENABLED);
> +
> +	if (IS_ENABLED(CONFIG_ARCH_HAS_MEM_ENCRYPT)) {

That's unconditionally enabled on x86:

	select ARCH_HAS_MEM_ENCRYPT

in x86/Kconfig.

Which sounds like you need a single XLF_MEM_ENCRYPT and simplify this
more.

> +		int on = cmdline_find_option_bool("mem_encrypt=on");
> +		int off = cmdline_find_option_bool("mem_encrypt=off");
> +
> +		if (on || off)
> +			hdr->xloadflags |= XLF_MEM_ENCRYPTION;
> +		if (on > off)
> +			hdr->xloadflags |= XLF_MEM_ENCRYPTION_ENABLED;
> +	}
> +}

Otherwise, I like the simplification.

Thx.

-- 
Regards/Gruss,
    Boris.

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