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

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Message-ID: <50C7795D.3000404@zytor.com>
Date:	Tue, 11 Dec 2012 10:20:13 -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>
Subject: Re: [tip:x86/microcode] x86/microcode_intel_early.c: Early update
 ucode on Intel's CPU

On 12/11/2012 10:02 AM, H. Peter Anvin wrote:
>
> The more I think about it, the more I think the right answer is the one
> we have pretty stated all along: if using the 64-bit entry point it is
> the responsibility of the boot loader to make sure the kernel, the setup
> data, and the initramfs are all mapped on entry.
>

This, in turn, brings up another major problem with the 64-bit entry 
point: right now it assumes page tables set up the way the current 
kernels expect them, but the way the kernel expects pages to be laid out 
on the future is almost guaranteed to change.  We need to formalize the 
expectations of the page table layout at 64-bit entry, and check to see 
what the implications of that are.

In particular, we may need to build a set of scaffolding page tables in 
the brk when entered from the 64-bit entry point and switch to them a 
lot sooner.  We wouldn't have to do that when coming from the 16/32-bit 
entry points since we'd control the layout of those page tables.

Oh how fun...

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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