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RE: [Xen-devel] [PATCH 0/3] Enable Option ROM support in Guest BIOS

To: 'John Levon' <levon@xxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH 0/3] Enable Option ROM support in Guest BIOS
From: "Shan, Haitao" <haitao.shan@xxxxxxxxx>
Date: Wed, 26 Nov 2008 10:08:43 +0800
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Thread-topic: [Xen-devel] [PATCH 0/3] Enable Option ROM support in Guest BIOS

Although we developed this for assigned devices, I think it also applies to 
emulated devices.

For adding support of an emulated SCSI device, I think there are different 
1> Modifies guest BIOS to directly support your emulated SCSI controller and 
devices. This does not need option ROM support.
2> Implement option ROM for your emulated devices. But loading of this option 
ROM can be hardcoded in HVMLoader, like current VGA BIOS in guest BIOS. This 
does not need generic option ROM support.
3> Implement option ROM for your emulated decices. Access this option ROM via 
PCI expansion BAR (of your emulated device of course). You can use this patches 
for loading and executing the option ROM. However, this alone can *not* enable 
booting from that SCSI device. You still need to modify guest BIOS to support 
BCV in BIOS Boot Specification.

So that answer to your question is: Yes, it helps towarding being able to boot 
from an emulated SCSI device for HVM guest if you choose to do it that way. But 
*not* enough. I do not know if there is anyone that is developing this 
capability. Maybe others who has interests on this can comment more.

Best Regards
Haitao Shan

John Levon wrote:
> On Mon, Nov 24, 2008 at 01:16:09PM +0800, Shan, Haitao wrote:
>> These three patches enables Option ROM support in guest BIOS. Please
>> see detailed description below. 
> Do these changes help towards being able to boot from an emulated SCSI
> device for HVM guests? Has any thought been done about that?
> regards
> john
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