Re: [Qemu-devel] Release plan for 0.12.0

[Gleb Natapov <gleb@redhat.com>]

On Fri, Oct 02, 2009 at 11:39:50PM +0200, Carl-Daniel Hailfinger wrote:
> > I'll bite, what's the advantage of doing coreboot + SeaBIOS vs.
> > SeaBIOS alone?  Forget about EFI for the moment, should be considering
> > switching to coreboot + SeaBIOS for 0.12?
> 
> Advantages:
> - Code coverage increase: SeaBIOS is used with coreboot on real
> hardware, so the BIOS interface part of SeaBIOS gets a lot more testing
> than the Qemu hardware init part of SeaBIOS.
> 
> - coreboot supports real 440BX hardware besides Qemu, so the coreboot
> init code is exercised more (and there is still a sizable number of such
> machines around (clusters), many of them running coreboot).
> 
QEMU goal is to run popular OSes and OS usually don't care about low level
chipset details. That's way QEMU's chipset emulation implements only
bare minimum that is needed for OS to run: no need to initialize memory
controller for instance. Coreboot goal, on the other hand, is to talk to
real HW, so to use it on QEMU will require implementing chipset features
that are not needed to accomplish QEMU goal. So for me real 440BX
hardware support of coreboot is actually disadvantage. QEMU don't
have real 440BX hardware and there is not point in having one. It is
possible to implement 440BX-qemu support in coreboot of course if there
are other advantages worth having.

> - Only one ROM image needed. A coreboot ROM can pack the VGA BIOS into
> the ROM image and SeaBIOS will automatically load it from there. Same
> for network card ROMs (with gPXE etc.).
> 
> - coreboot ROMs (including those with SeaBIOS and/or EFI and/or VGABIOS)
> are archives and can be listed/edited with cbfstool if you want to know
> what's in there.
> 
> - coreboot ROMs use compression, so you can stuff more code (and PCI
> option ROMs) into smaller ROMs.
> 
> - coreboot has pretty verbose hardware init messages (if you want that)
> and can be totally silent as well. The messages end up in a log buffer
> which can be read by the OS (experimental feature, not available by
> default).
> 
> There are a lot more advantages, but I want to give other coreboot
> developers a chance to chime in. If you add EFI to the mix, the
> synergies increase.
> 
> 
> Regards,
> Carl-Daniel
> 

--
			Gleb.