linux-kernel - RE: Early microcode signing in secure boot environment - Was: x86, microcode: Use common get_ramdisk

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Date:	Wed, 10 Apr 2013 17:47:25 +0000
From:	"Yu, Fenghua" <fenghua.yu@...el.com>
To:	Thomas Renninger <trenn@...e.de>,
	Tang Chen <tangchen@...fujitsu.com>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: Early microcode signing in secure boot environment -  Was: x86,
 microcode: Use common get_ramdisk_image()

> -----Original Message-----
> From: Thomas Renninger [mailto:trenn@...e.de]
> Sent: Wednesday, April 10, 2013 12:41 AM
> Hello,
> 
> On Wednesday, April 10, 2013 01:34:33 PM Tang Chen wrote:
> > On 04/05/2013 07:46 AM, Yinghai Lu wrote:
> > > Use common get_ramdisk_image() to get ramdisk start phys address.
> > >
> > > We need this to get correct ramdisk adress for 64bit bzImage that
> > > initrd can be loaded above 4G by kexec-tools.disk_size;
> 
> don't know whether this question came up when this feature got
> submitted (if yes a pointer would be appreciated).
> 
> Is there a concept how signed microcode can get verified when applied
> early,
> like it is done via firmware loader?
> 
> If not, early microcode loading is not really usable in secure boot
> environment, right?

The microcode is cryptographically authenticated by the CPU itself, so there is no security issue related to early microcode loading.

Thanks.

-Fenghua

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