Re: [Qemu-devel] [PATCH] turn firmware image filename into a machine option

[Alexander Graf <agraf@suse.de>]

On 10/01/2013 04:40 PM, Gerd Hoffmann wrote:
>    Hi,
>
>> SLOF is what is loaded from the very beginning, it configures PCI, cooks
>> the device tree and boots the guest system (directly or via yaboot/grub,
>> from disk, network or ram). Normal firmware, as usual. It knows all the
>> details about the machine so the guest system (linux) does not need to know
>> details about PCI host bus adapter or anything like this.
> So pretty much like seabios on x86.
>
>> RTAS is an agent which always lives in RAM when the guest system (linux,
>> aix) is up and running. It is a light-weight version of SLOF which is left
>> in RAM by SLOF and can do board/machine specific tasks such as PCI config
>> space access or PCI hotplug - something what SLOF already knows about and
>> something what the guest does not want to know about in details. This came
>> from IBM pHyp (traditional server PPC64 hypervisor) and it is quite a big
>> firmware. In the case of KVM, it is very small stub which simply passes
>> requests to QEMU which does the rest. But it is still a separate binary
>> image even in the current QEMU.
> How that does get loaded?  Is it there at machine init?  Or does SLOF
> load RTAS from somewhere?

It gets loaded to a fixed address similar to the device tree. But 
there's no reason that couldn't be changed to on demand loading or even 
an integrated RTAS blob inside of SLOF.


Alex