linux-kernel - Re: [PATCH 0/2] x86/microcode: support for microcode update in Xen dom0

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Date:	Wed, 02 Feb 2011 13:47:18 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Ingo Molnar <mingo@...e.hu>,
	the arch/x86 maintainers <x86@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Xen Devel <Xen-devel@...ts.xensource.com>,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: Re: [PATCH 0/2] x86/microcode: support for microcode update in Xen
 dom0

On 02/02/2011 12:57 PM, Borislav Petkov wrote:
> On Wed, Feb 02, 2011 at 11:52:22AM -0800, H. Peter Anvin wrote:
>> 3. Arguably on native hardware we should still load the microcode into
>> RAM in the boot loader, and install it on the very early CPU bringup
>> path.  That means locking down some (currently) 400K of RAM to handle
>> different combinations of CPUs, or the additional complexity of
>> jettisoning microcode which cannot be used while still be able to deal
>> with hotplug.  I think there is a strong case for this model, which
>> would mean moving the microcode into /boot anyway.
> 
> /me like it, sounds very nifty. So how do we want to do that, we add
> a field to the real-mode kernel header that tells us where to find
> the microcode image and we take it and apply the ucode somewhere in
> do_boot_cpu() path?
> 

We already have a mechanism for passing arbitrary blobs -- the linked
list -- so we don't have to add a new field at all.

	-hpa

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