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

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Message-ID: <CAE9FiQW_mjUr6F0q7PhZWCcDzZ+NJpi0-xjxvwJoZ1K+XAUjSQ@mail.gmail.com>
Date:	Mon, 24 Dec 2012 20:04:18 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
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 Mon, Dec 24, 2012 at 4:16 PM, H. Peter Anvin <hpa@...or.com> wrote:
> 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.

well, I updated for-x86-boot-v7 that stop #PF handler after init_mem_mapping.

it has fix for AMD system aka reverting far jmp to ret.

Yinghai
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