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

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Date:	Thu, 21 Jun 2012 01:46:11 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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 Wed, Jun 20, 2012 at 04:34:17PM -0700, H. Peter Anvin wrote:
> On 06/20/2012 04:32 PM, Borislav Petkov wrote:
> > 
> > Which means that
> > 
> > static enum ucode_state request_microcode_fw(int cpu, struct device *device)
> > {
> >         char name[30];
> > 
> > 	...
> > 
> >         sprintf(name, "intel-ucode/%02x-%02x-%02x",
> >                 c->x86, c->x86_model, c->x86_mask);
> > 
> > needs to be changed to the name of the microcode blob you guys use for
> > distributing and we can drop the OLD INTERFACE and there'll be no need
> > for userspace tools doing anything with the ucode patches.
> > 
> 
> 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.

-- 
Regards/Gruss,
Boris.

Advanced Micro Devices GmbH
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