linux-kernel - Re: microcode loading got really slow.

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Message-ID: <20130523155532.GE16419@redhat.com>
Date:	Thu, 23 May 2013 11:55:32 -0400
From:	Dave Jones <davej@...hat.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	Takashi Iwai <tiwai@...e.de>, "H. Peter Anvin" <hpa@...or.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>, x86@...nel.org,
	fenghua.yu@...el.com
Subject: Re: microcode loading got really slow.

On Thu, May 23, 2013 at 11:27:08PM +0800, Ming Lei wrote:
 > > Yes, in your case, everything is fine in the kernel itself.  And no
 > > microcode update is needed for new CPU, thus no firmware.
 > 
 > Can the driver decide if the CPU need microcode? Or there will
 > be the microcode for the CPU in future?

The kernel can't know. The microcode updates are asynchonously released
from the kernel. I might be running a months old kernel, and get a new
microcode tomorrow.  The kernel handles this by looking for a file
with a name matching the cpu family/model/stepping. (See how they are
formed in /lib/firmware/intel-ucode/*)

	DAve

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