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Subject: RE: [PATCH 5/5] x86_64 EFI support -v3: EFI document
Date: Wed, 8 Aug 2007 21:46:15 +0800
Message-ID: <9D7649D18729DE4BB2BD7B494F7FEDC246DC2B@pdsmsx415.ccr.corp.intel.com>
In-Reply-To: <200708081208.01080.ak@suse.de>
Thread-Topic: [PATCH 5/5] x86_64 EFI support -v3: EFI document
Thread-Index: AcfZpEOubAzrT1rySEufv4w2F4alhgAGkKIg
From: "Huang, Ying" <ying.huang@intel.com>
To: "Andi Kleen" <ak@suse.de>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>, <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>
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1580
Lines: 41

>-----Original Message-----
>From: Andi Kleen [mailto:ak@suse.de]
>Subject: Re: [PATCH 5/5] x86_64 EFI support -v3: EFI document
>> The needed code changing is minimal. In fact, I can boot 32bit Linux
>> kernel on my x86_64 EFI machine. With setup as follow:
>>
>> 1. Apply the efi-fb.patch
>Just for the frame buffer, right?

Yes.

>> 2. make efi fb driver not depend on EFI
>> 3. configure kernel as follow:
>>    a. CONFIG_EFI is turned off
>>    b. CONFIG_FB_EFI is turned on
>
>Hmm, how does the 32bit kernel know where the e820 map is passed then?
>With CONFIG_EFI turned off it will just ask the real mode BIOS I think
>and I doubt elilo simulates that.

I have not tested elilo. I use another x86_64 EFI boot loader (it will
be released soon), but elilo works in the same way, and I will test
elilo later. The 16bit entry of kernel (arch/(i386|x86_64)/boot/setup.S)
is not used by elilo. Instead, elilo collects the needed information
defined in include/asm-x86_64/bootsetup.h itself, and passes it to
kernel 32bit entry (arch/(i386|x86_64)/boot/compressed/head.S). For E820
map, the elilo converts the EFI memory map to E820 map in "boot
parameters memory" which is copied to "boot_params" or "x86_boot_params"
by Linux kernel later.

>Or did you apply more patches?

No, just the frame buffer patch.

Best Regards,
Huang Ying
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