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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 01 Oct 2013 16:40:23 +0200
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Subject: Re: [Qemu-devel] [PATCH] turn firmware image filename into a
	machine option
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To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: Peter Maydell <peter.maydell@linaro.org>, Mark Langsdorf <mark.langsdorf@calxeda.com>, QEMU Developers <qemu-devel@nongnu.org>, Fabien Chouteau <chouteau@adacore.com>, Alexander Graf <agraf@suse.de>, Blue Swirl <blauwirbel@gmail.com>, Michael Walle <michael@walle.cc>, =?ISO-8859-1?Q?Herv=E9?= Poussineau <hpoussin@reactos.org>, Paul Brook <paul@codesourcery.com>, Anthony Liguori <anthony@codemonkey.ws>, qemu-ppc <qemu-ppc@nongnu.org>, Andreas =?ISO-8859-1?Q?F=E4rber?= <afaerber@suse.de>, Aurelien Jarno <aurelien@aurel32.net>, Richard Henderson <rth@twiddle.net>

  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?

thanks,
  Gerd