linux-kernel - Re: [patch 05/11] [PATCH 05/11] x86: Moved microcode.c to microcode

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Date:	Fri, 19 Sep 2008 07:29:21 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	"Giacomo A. Catenazzi" <cate@...ian.org>
Cc:	Peter Oruba <peter.oruba@....com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tigran Aivazian <tigran@...azian.fsnet.co.uk>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [patch 05/11] [PATCH 05/11] x86: Moved microcode.c to
 microcode_intel.c.

On Fri, 19 Sep 2008 16:06:53 +0200
"Giacomo A. Catenazzi" <cate@...ian.org> wrote:

> Peter Oruba wrote:
> > Giacomo A. Catenazzi schrieb:
> >> Dmitry Adamushko wrote:
> >>> 2008/9/19 Peter Oruba <peter.oruba@....com>:
> >>>> Some additonal words regarding the current user space issues:
> >>>>
> >>>> IMHO the most convenient way to update microcode is through the
> >>>> firmware loading
> >>>> interface instead of microcode_ctl. This reduces user-space
> >>>> responsibilities to
> >>>> loading the correct module at boot time and to place the
> >>>> microcode patch file at
> >>>> the right location via package installation. The problems
> >>>> mentioned in this
> >>>> thread would then probably disappear as well. What do you guys
> >>>> think?
> >>> It'd still require changes for all the setups that currently rely
> >>> on the 'microcode_ctl' interface. Moreover, Arjan's setup failed
> >>> not due to the 'microcode_ctl' per se but due to the altered
> >>> kernel module name. After all, we can't break the established
> >>> interface this way.
> >>>
> >>> We can either reserve 'microcode' as a legacy name for intel cpus
> >>> (== microcode_intel), or maybe we can use request_module() from
> >>> microcode.ko to load a proper arch-specific module (I guess, it's
> >>> not ok for !KMOD-enabled kernels).
> >> I agree. A wrapper "microcode.ko" module would be nice, in order
> >> to allow independent kernel and user space upgrades.
> >>
> >> The module name is important also on udev method: only a module
> >> load triggers the microcode request in udev, thus also the
> >> new method should have stable kernel module name.
> >>
> >> ciao
> >>     cate
> >>
> > 
> > That sounds like a single-module solution would be the best way to
> > go. All dependencies would then be handled inside the module.
> 
> Single module probably is more difficult to maintain.
> 
> I was thinking about a very simple additional module:
> It checks the cpu: load the relevant module, and wrapper the
> calls to the relevant module.
> 
> So every vendor could develop easier the own driver. Only the
> interface should be stable.
> 
> Eventually we could solve it in the distribution scripts (using module
> aliases), but it would be kernel version dependent, and it would works
> only on the new method (or a new microcode_ctl version, but people
> upgrade more often kernel than packages).

this would still fail the fedora microcode_ctl scripts; those also do
an rmmod afterwards, which now will fail with our method

what a mess ;-(

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
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