Re: [Xen-devel] [PATCH 2/2] x86/microcode: enable boot time (pre-Dom0) loading

[Tim Deegan <tim@xxxxxxx>]

At 18:23 -0400 on 30 Nov (1322677439), Konrad Rzeszutek Wilk wrote:
> On Wed, Nov 30, 2011 at 04:27:11PM +0000, Jan Beulich wrote:
> > Largely as a result of the continuing resistance of Linux maintainers
> > to accept a microcode loading patch for pv-ops Xen kernels, this
> > follows the suggested route and provides a means to load microcode
> > updates without the assistance of Dom0, thus also addressing eventual
> > problems in the hardware much earlier.
> > 
> > This leverages the fact that via the multiboot protocol another blob
> > of data can be easily added in the form of just an extra module. Since
> > microcode data cannot reliably be recognized by looking at the
> > provided data, this requires (in the non-EFI case) the use of a
> > command line parameter ("ucode=<number>") to identify which of the
> 
> Well, usually there would be two modules - the kernel (which we can
> identify) and the initramfs (which I guess one can also identify)?
> It seems that by process of elimination we could determine that the
> remaining module is the blob?

I'd really rather not do it that way - what if you want no initrd but do
have a microcode update? :)  And what if we want to add another
special-purpose multiboot module later?

It might be nice if that number could take negative values, though -
i.e. ucode=-1 to say 'use the last module in the list'.  Then the user
could adjust the dom0 modules without needing to recalculate.

Tim.

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