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 11:18:35 -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>
Subject: Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update
 ucode on Intel's CPU

On Tue, Dec 11, 2012 at 10:46 AM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/11/2012 10:42 AM, Yinghai Lu wrote:
>>
>> now in for-x86-boot:
>> http://git.kernel.org/?p=linux/kernel/git/yinghai/linux-yinghai.git;a=commit;h=8e4e093e6d140f1316953437fdde4e826f5cfd98
>>
>> it adds extra mapping from the whole kernel when kernel is loaded above 1G.
>> from round_down(_text, 2M) to round_up(_end -1, 2M).
>>
>> Do you mean we need to add extra mapping for realmode_data, cmdline,
>> ramdisk too? (not include setup_data, and it is accessed via
>> early_ioremap later).
>
> Yes, but...

that will be bunch of asm code again, and need to parse the setup_header in that
asm to get range value for those regions...

>
>> but if the user memmap to exclude some page, we will still need to
>> relocate the ramdisk.
>
> -ENOPARSE

.. I mean pointer for saved ucode will be updated then again.
and relocated_initrd wil still need to use ioremap because init_memory_mapping
will clean mapping the range range that is excluded by memmap=XX$YY

>
> I really need to look at this in more detail.  I'm starting to think
> this is done completely backwards.

really should not put asm code if it could be done in C in not complicated way.
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