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Date: Thu, 15 Feb 2007 00:12:30 +0100
From: Fabrice Bellard <fabrice@bellard.org>
Subject: Re: [Qemu-devel] Re: [PATCH] LinuxBIOS support: map BIOS into ISA
	address space as RAM instead of ROM
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To: eswierk@arastra.com
Cc: qemu-devel@nongnu.org

Ed Swierk wrote:
> On 2/13/07, Ed Swierk <eswierk@arastra.com> wrote:
> 
>> This patch changes qemu to map the BIOS into ISA address space as RAM
>> instead of ROM, allowing LinuxBIOS to run on qemu with no further
>> modifications (although the DRAM size is still not detected properly).
> 
> 
> Unfortunately this isn't the right answer, as modifying the BIOS area
> messes things up on soft reboot. What we really want is shadow RAM
> support, which Bochs seems to support but qemu doesn't.

Shadow RAM is supported in QEMU and I modified the Bochs BIOS to use it. 
So you do not need to do any patch in QEMU for it. Please read the 
rombios32.c source in the Bochs BIOS to know what to do in LinuxBIOS.

To be precise, one case of RAM shadowing is not implemented (read from 
BIOS, write to RAM), but it is not strictly needed to write data in the 
shadow RAM. I needed it once to run a real Award BIOS in QEMU, but I did 
not have the time to clean up the patch to commit it.

Regards,

Fabrice.