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Date: Wed, 21 Nov 2012 12:16:05 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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Subject: Re: [PATCH v3 4/4] kexec, x86_64: Load bzImage64 above 4G
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To: Yinghai Lu <yinghai@kernel.org>
Cc: Haren Myneni <hbabu@us.ibm.com>, Simon Horman <horms@verge.net.au>, kexec@lists.infradead.org, "Eric W. Biederman" <ebiederm@xmission.com>, Vivek Goyal <vgoyal@redhat.com>

On 11/21/2012 12:01 PM, Yinghai Lu wrote:
> On Wed, Nov 21, 2012 at 11:56 AM, H. Peter Anvin <hpa@zytor.com> wrote:
>> On 11/21/2012 11:54 AM, Yinghai Lu wrote:
>>>
>>> in kernel arch/x86/kernel/head_64.S
>>>
>>> it only set first 1G ident mapping. and if it find that code is above
>>> 1G, it will set extra ident mapping
>>> for new _text.._end.
>>> To make checking and add extra mapping simple and also save two extra
>>> pages for mapping.
>>> Limit that _text.._end in them same GB range.
>>>
>>
>> No, this is backwards.
> 
> old one: it limited bzImage in [0,1G) aka the first 1G.
> 
> Now we can put it in any aligned 1G range.
> 
> So how could it be called backwards?
> 

Because you're adding a more complicated hack.

>>
>> We should fix that limitation instead.
> 
> sure, but that will make arch/x86/boot/compressed/head_64.S not need
> complicated.
> 

But it makes the bootloaders more complicated, and the bootloaders are
harder to fix.

	-hpa


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