[Qemu-devel] Re: [PATCH 0/4] ppc: Fix PReP emulation

[Alexander Graf]

On 20.12.2010, at 13:19, François Revol wrote:

>>>> So we certainly do need some open source firmware solution for prep to at 
>>>> least have Linux running. For other guests, I don't see a reason why users 
>>>> shouldn't try to fetch a real firmware blob separately :).
>>> 
>>> We're not shipping any firmware for ppcemb either, so that argument seems 
>>> moot. OpenBIOS, SeaBIOS and ZIPL are the only ones currently. Feel free to 
>>> supply additional blobs for U-Boot etc.
>> 
>> IIUC you don't need u-boot for the embedded targets. You just pass in a 
>> kernel and the rest is magic.
> 
> This holds only for Linux which imposes its own startup API to bootloaders 
> and go with kernel drivers directly.
> 
> Other OS like Haiku use a 2nd stage bootloader which assumes a working 
> callable BIOS (OF on ppc), and getting it to run on U-Boot is already tricky 
> on its own.

That was my point :). I'm not aware of us supporting firmware on ppcemb, so 
it's capable of running an OS all by itself already.

> 
>>> Recent vanilla Linux kernels wouldn't run on PReP. So what Linux do you 
>>> want to run using open source firmware?
>>> I certainly do not intend to write firmware for the upcoming 40p machine. 
>>> If Linux runs on real 40p hardware then it should run with real firmware 
>>> under emulation, too. QEMU is an emulation project, not a Linux testing 
>>> framework.
>> 
>> I completely agree. Linux is usually easy because it's fully open source and 
>> supports a lot of targets. If you feel like running NetBSD or Haiku instead, 
>> feel free to do so.
> 
> Thanks for thinking about Haiku ;)
> 
> Btw there are other existing targets, like AROS, MorphOS, or AmigaOS which 
> uses a modified U-Boot with a 'boota' command that passes their 2nd stage 
> Parthenope bootloader a list of BIOS-like callbacks into U-Boot, cf. :
> http://www.acube-systems.biz/index.php?page=hardware&pid=2
> http://www.acube-systems.biz/download/u-boot-1.3.1c_20101206_prod.tar.gz
> 
> Though they probably won't run on PReP, and PReP support in Haiku might come 
> only for the sake of supporting the BeBox, which had its own dumb firmware 
> (MAME seems to have some emulation support for BeBox).
> 
> OTOH, I've been thinking about adding a Sam440 target, but it'd still require 
> the custom U-Boot to start AmigaOS for example.

I'd call U-Boot the firmware that we can ship with Qemu then because it's open 
source :). I'm not advocate for openBIOS. If it works, great. If something else 
works better, let's take that.

The only thing I really want to see is a target that does something useful. 
That's it :). A target that loads proprietary firmware halfway through is not 
valuable to users IMHO. A target that loads proprietary firmware and boots an 
OS is valuable. A target that doesn't need firmware and loads an OS is 
valuable. Maybe a target that doesn't boot an OS quite yet, but loads open 
source firmware pretty well is valuable too.


Alex