linux-kernel - Re: [PATCH 2/2] x86, microcode: Make reload interface per system

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Date:	Wed, 20 Jun 2012 16:48:37 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...64.org>
CC:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Peter Zijlstra <peterz@...radead.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>, X86-ML <x86@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>
Subject: Re: [PATCH 2/2] x86, microcode: Make reload interface per system

On 06/20/2012 04:46 PM, Borislav Petkov wrote:
>>
>> Except you still need to re-poke it when you have a new microcode
>> blob... so what was gained by all this churn?
> 
> We need to do that anyway if new (F,M,S) ucode piece comes along.
> 
> The gain is twofold:
> 
> * we don't need the userspace tool to split the blob - we have one
> single file we load and the driver picks out what it needs.
> 
> * as a result, we drop the CONFIG_MICROCODE_OLD_INTERFACE, i.e.
> /dev/cpu/microcode which takes the single blob anyway which the driver
> picks apart later.
> 
> In the end, we have one unified ucode loading procedure:
> 
> 1. put the blob in /lib/firmware/...
> 2. echo 1 > /sys/devices/system/cpu/microcode/reload
> 
> That's it - it can't be simpler than that.
> 

I really don't get why the whole thing is any simpler than the old
/dev/cpu/microcode interface in the first place, where instead of:

> 1. put the blob in /lib/firmware/...
> 2. echo 1 > /sys/devices/system/cpu/microcode/reload

... you do ...

1. dd if=<microcode blob> of=/dev/cpu/microcode bs=<large>

... as well as set up the early initramfs part, of course.

	-hpa



-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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