[Qemu-devel] Re: [PATCH 0/2] port over extboot from kvm

[Jan Kiszka <jan.kiszka@siemens.com>]

Gerd Hoffmann wrote:
> $subject says pretty much everything.
> 
> extboot.[cS] are a straight copy from the kvm tree.  The windup in vl,c
> and hw/pc.c is done slightly different, I've added a function to lookup
> the boot drive instead of adding a new global variable.
> 
> Booting from scsi and virtio works, using the boot=on flag.
> 
> With the usb+scsi patches in anthonys patch queue applied booting from
> usb works too.  Syntax is this:
> 
> 	-drive if=none,id=pendrive,file=/path/to/image,boot=on
> 	-usb -device usb-storage,drive=pendrive
> 
> Booting a rawhide install from a virtual usb stick doesn't actually work
> though, looks like it stresses qemus usb emulation too much.
> 

Before setting this definitely useful feature in stone, I have two
questions though:

 - -drive ...,boot=on is logically in conflict with -boot. Yes, -boot
   for x86 currently cannot differentiate between multiple disks, only
   between boot media types. Still, this two-stage configuration is
   rather unintuitive and looks like a patchwork. Given that we have
   full control over all components, is it really the preferred
   approach? I already thought about, e.g., -boot c2 to select the
   second disk. Not that nice, but I would rather vote for a consistent
   configuration than a scattered one.

 - This is just an implementation detail: Do we really need to implement
   booting from virtio and scsi via an extension rom? Isn't it possible
   to merge the corresponding support into the main bios?

Jan

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