linux-kernel - Re: [PATCH v5 00/12] x86/microcode: Early load microcode

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Date:	Wed, 9 Jan 2013 08:35:56 -0500
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Fenghua Yu <fenghua.yu@...el.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Asit K Mallick <asit.k.mallick@...el.com>,
	Tigran Aivazian <tigran@...azian.fsnet.co.uk>,
	Yinghai Lu <yinghai@...nel.org>,
	Andreas Herrmann <andreas.herrmann3@....com>,
	Borislav Petkov <borislav.petkov@....com>,
	linux-kernel <linux-kernel@...r.kernel.org>, x86 <x86@...nel.org>
Subject: Re: [PATCH v5 00/12] x86/microcode: Early load microcode

On Tue, Jan 08, 2013 at 03:04:33PM -0500, Konrad Rzeszutek Wilk wrote:
> On Tue, Jan 08, 2013 at 11:47:39AM -0800, H. Peter Anvin wrote:
> > On 01/08/2013 11:46 AM, Konrad Rzeszutek Wilk wrote:
> > > 
> > > OK. I am trying to figure out whether this usage of native_* for the
> > > MSRs was done on purpose - and it sounds like the answer is no. If so -
> > > can it be done using the normal 'safe_rdmsr' and 'wrmsr'?
> > > 
> > > That would allow at least in the case of Xen, to omit a whole bunch
> > > of MSR writes/reads during the boot that are not neccessary as we would
> > > not trap in the hypervisor - but could use the pvops version of
> > > read/write MSR calls to just do a nop.
> > > 
> > 
> > Why is this code invoked on Xen at all?  That seems crazy.
> 
>  [PATCH v4 09/11] x86/head64.c: Early update ucode in 64-bit
> 
> has this in x86_64_start_kernel:
> 
> ..
>         load_idt((const struct desc_ptr *)&idt_descr);
> 
> +       /*
> +        * Load microcode early on BSP.
> +        */
> +       load_ucode_bsp(__va(real_mode_data));
> +
>         copy_bootdata(__va(real_mode_data));
> 
> Which gets called after xen_start_kernel has setup pagetables,
> bootparams, etc ready for the generic code to be invoked.

And I am looking at the wrong code. The "x86_64_start_kernel" is
absolutly fine. It is "x86_64_start_reservations" that is invoked by Xen.

I got thrown off by the "copy_bootdata(.." which on v3.7 is in
"x86_64_start_reservations".

Duh!
> 
> Or am I looking at an old version of these patches.
> > 
> > 	-hpa
> > 
> > 
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