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 15:53:01 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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 Tue, Dec 11, 2012 at 9:38 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/11/2012 09:15 AM, Yinghai Lu wrote:
>>
>>
>> No, that is not right place. initrd could be loaded anywhere like way
>> high by bootloader.
>>
>
> Only *after* your changes... the current protocol doesn't allow that.

before for-x86-boot change,

bootloader put ramdisk just under 2g...

[    0.000000] memblock_reserve: [0x7d9dc000-0x7fffefff] RAMDISK

and arch/x86/kernel/head_64.S only set ident mapping for [0,1g)

so before init_memory_mapping, we need to use early_ioremap to access
ramdisk area.

also even after init_memory_mapping, we still need use early_ioremap to access
it because user could use memmap to skip it.

PS: this problem have nothing to do with mapping that is set by bootloader.
arch/x86/kernel/head_64.c will have it own mapping, and only cover [0,1g).

Yinghai

>
> Anyway, we need to deal with it, see below.
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