linux-kernel - Re: [PATCH v7 06/27] x86, 64bit: early #PF handler set page table

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Message-ID: <50D8F054.20404@zytor.com>
Date:	Mon, 24 Dec 2012 16:16:20 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Jason Wessel <jason.wessel@...driver.com>,
	Jan Kiszka <jan.kiszka@....de>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 06/27] x86, 64bit: early #PF handler set page table

On 12/20/2012 08:56 AM, Yinghai Lu wrote:
>>
>> So in that case, kgdb is broken and will need to be fixed up.  That
>> happens all the time with debugging tools.
>
> If there is a way that we can make all parties happy, we really should
> not break KGDB.
>
> Please reconsider to stop #PF handler in x86_64_start_kernel. in that case
> 1. microcode update still can use #PF handler to find microcode in
> ramdisk and use it.
> 2. kernel that is loaded above 4G, could set mapping in C instead of
> set that in head_64.S
>     and use ioremap to access zero_page
> 3. KGDB still can call early_trap_init early before init_mem_mapping.
>

Yinghai, this is total and utter bullshit.

We should *fix* kgdb, not pave around it.  I refuse to have kgdb be yet 
another Xen turning random kernel internals into ABIs.

	-hpa

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

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