linux-kernel - Re: [PATCH 04/11] x86/microcode_core_early.c: Define interfaces for early load ucode

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Date:	Sat, 18 Aug 2012 19:44:42 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	Fenghua Yu <fenghua.yu@...el.com>
Cc:	H Peter Anvin <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Asit K Mallick <asit.k.mallick@...el.com>,
	Tigran Aivazian <tigran@...azian.fsnet.co.uk>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH 04/11] x86/microcode_core_early.c: Define interfaces
 for early load ucode

On Sat, 18 Aug 2012, Fenghua Yu wrote:
> +	char ucode_name[] = "kernel/x86/microcode/GenuineIntel/microcode.hex";

Why name it ".hex" when you're loading binary data?  I suggest ".bin".  It
is confusing to have .hex there, since you're not dealing with the Intel HEX
format, nor anything text-like.

> +void __init load_ucode_bsp(char *real_mode_data)
> +{
> +	u64 ramdisk_image, ramdisk_size, ramdisk_end;
> +	unsigned long initrd_start, initrd_end;
> +	struct boot_params *boot_params;
> +
> +	boot_params = (struct boot_params *)real_mode_data;
> +	ramdisk_image = boot_params->hdr.ramdisk_image;
> +	ramdisk_size  = boot_params->hdr.ramdisk_size;
> +
> +#ifdef CONFIG_X86_64
> +	ramdisk_end  = PAGE_ALIGN(ramdisk_image + ramdisk_size);
> +	initrd_start = ramdisk_image + PAGE_OFFSET;
> +#else
> +	ramdisk_end  = ramdisk_image + ramdisk_size;
> +	initrd_start = ramdisk_image;
> +#endif
> +	initrd_end = initrd_start + ramdisk_size;
> +
> +	/*
> +	 * It's early to get CPU vendor info at this point.
> +	 * By searching initrd to find right name for vendor's microcode,
> +	 * it's relative easier to get CPU vendor info.
> +	 */
> +	if (find_ucode_intel(initrd_start, initrd_end) == UCODE_OK)
> +		load_ucode_intel_bsp(real_mode_data);
> +}

I'd say something down the load_ucode_intel_bsp() chain better check the CPU
vendor to make sure the Intel driver won't attempt to load microcode on some
other vendor's processor.

Or are cpu signatures a global namespace and x86 cpu vendors make sure
(past, present and future) to never use the same cpu signature as someone
else is going to use?  Anyway, it would still might be a good thing to do
the vendor check somewhere to avoid wasting time going over every microcode
of the wrong vendor on generic boot images that have both AMD and Intel
microcode.

-- 
  "One disk to rule them all, One disk to find them. One disk to bring
  them all and in the darkness grind them. In the Land of Redmond
  where the shadows lie." -- The Silicon Valley Tarot
  Henrique Holschuh
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