Subject: Re: [PATCH 5/5] x86_64 EFI support -v3: EFI document
From: "Huang, Ying" <ying.huang@intel.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: ak@suse.de, akpm@linux-foundation.org, Yinghai Lu <yhlu.kernel@gmail.com>,
       Randy Dunlap <randy.dunlap@oracle.com>,
       Chandramouli Narayanan <mouli@linux.intel.com>,
       linux-kernel@vger.kernel.org
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	 <m1r6mnnpj8.fsf@ebiederm.dsl.xmission.com>
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Date: Tue, 07 Aug 2007 17:29:44 +0800
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On Thu, 2007-08-02 at 01:16 +0800, Eric W. Biederman wrote:
> > The parameters are rearranged, because the pointer is too small. For
> > example, the EFI system table pointer is 8 bytes in x86_64, while it
> is
> > 4 bytes in i386.
> 
> Ok.  I see what is happening.  When the documentation is for arch/i386
> unsigned long is 4 bytes, and you are using unsigned long to mean 8
> bytes.  For an 8 byte fields please just spell out the size as 8
> bytes.

Ok. Will do in the next version.
> 
> How does EFI handle 32bit/64bit compatibility?  In particular
> how do I load a 32bit kernel on machine with a 64bit EFI?  Can
> it be done?
> 
Because the EFI memory map is converted to E820 map in bootloader now,
it is possible to load 32bit kernel on machine with a 64bit EFI. But it
is almost impossible to call EFI runtime service in 32bit kernel. But I
think EFI runtime service is not essential in this situation, because
the raw hardware can be used too.

Best Regards,
Huang Ying
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