linux-kernel - Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update ucode on Intel's CPU

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Date:	Tue, 11 Dec 2012 16:37:35 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Borislav Petkov <bp@...en8.de>,
	"Yu, Fenghua" <fenghua.yu@...el.com>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"hpa@...ux.intel.com" <hpa@...ux.intel.com>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Stefano Stabellini <Stefano.Stabellini@...citrix.com>
Subject: Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update
 ucode on Intel's CPU

On 12/11/2012 04:27 PM, Yinghai Lu wrote:
> On Tue, Dec 11, 2012 at 3:57 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> Well, we could invoke it on the bootloader page tables, but as you say
>> it may not be a good idea... depending on how much memory we may be
>> talking about.  One solution -- which I have to admit is starting to
>> sound really good -- is to set up a #PF handler which cycles through a
>> set of page tables and creates a "virtual identity map"... it does have
>> the advantage of making the entire physical address space available
>> without any additional funnies.
> 
> so that #PF handler will work before
> arch/x86/kernel/setup.c::setup_arch/early_trap_init
> 
> early_strap_intit will install another handler there for #PF
> 
> for 64bit, moving early_ioremap_init ahead is very simple, like attach patch
> 
> but for 32 bit looks like it is not that easy.
> 

For 32 bits, we don't need it, because we can just run this part in
linear mode.  It also doesn't help us on 32 bits since we are limited by
virtual address space anyway.

	-hpa

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