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

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Date:	Wed, 20 Jun 2012 21:06:31 -0300
From:	Henrique de Moraes Holschuh <hmh@....eng.br>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...64.org>,
	LKML <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Greg Kroah-Hartman <greg@...ah.com>,
	"Yu, Fenghua" <fenghua.yu@...el.com>
Subject: Re: [PATCH] x86, microcode: Make reload interface per system

On Wed, 20 Jun 2012, H. Peter Anvin wrote:
> On 06/20/2012 04:46 PM, Henrique de Moraes Holschuh wrote:
> > Well, it makes the kernel tell us what (amd/intel/whatever) firmware it
> > wants, and requires (after patching) a simple echo 1 >foo to activate.  It
> > is also harmless if activated without updated firmware in place.
> > 
> > /dev/cpu/microcode requires special software (or a dd with bs>=file size),
> > since it borks if userspace breaks a microcode into two write() syscalls,
> > and requires detection of the cpu vendor.  Very annoying.
> > 
> 
> Yeah, because dd is such an exotic piece of software...

No, because dd if=<whatever> of=/dev/cpu/microcode bs=1M means I have to
add dd to the initramfs or to busybox, AND it will break the day the
microcode data file gets bigger than 1M.  And it will be at best very
annoying to have to special case each vendor to locate the correct
microcode, etc.

I'll take the firmware interface we already have to support to get
anything done with a lot of other drivers anyway, thank you very much.

-- 
  "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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