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Date: Wed, 9 Jan 2013 08:35:56 -0500
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Konrad Rzeszutek Wilk <konrad@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Fenghua Yu <fenghua.yu@intel.com>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
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        Yinghai Lu <yinghai@kernel.org>,
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        Borislav Petkov <borislav.petkov@amd.com>,
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Subject: Re: [PATCH v5 00/12] x86/microcode: Early load microcode
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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
> > 
> >