[Qemu-devel] What is qemu-system-ppcemb for?

[Qemu-devel] What is qemu-system-ppcemb for?

[Rob Landley]

The qemu-system-ppcemb binary has the same -M and -cpu options as qemu-system-
ppc.  The default-configs/*.mak files are identical for ppc-softmmu.mak and 
ppcemb-softmmu.mak.  The ppc-softmmu/config-target.mak matches the one in 
ppcemb-softmmu.  The "config-target.mak" files differ, but just in the names.

I looked at the source code and hw/ppc.c shows "Embedded PowerPC timers" for 
things like cpu_4xx_fit_cb(), but those seem to be used by the standard qemu-
system-ppc...

So far the only actual difference I've tracked down is that  target-ppc/cpu.h 
is setting TARGET_PAGE_BITS to 10 (for 1k pages) instead of 12 (4k pages)... 
except it's not doing that for CONFIG_USER_ONLY...?  (For KVM, it's assuming a 
ppc4xx CPU by default, but I'm not using kvm.)

I tried booting my ppc image with qemu-system-ppcemb instead and it hung, so 
something's different.  Presumably that page size thing...

Has anybody actually used ppcemb for anything?  Is there a Linux config or it?  
I've been building a powerpc4xx system image, but booting it under g3beige 
because last I checked qemu doesn't emulate a 4xx processor?  (It has a bamboo 
board, but only lets you use it under kvm...)

Confused,

Rob 
-- 
Latency is more important than throughput. It's that simple. - Linus Torvalds

Re: [Qemu-devel] What is qemu-system-ppcemb for?

[Nathan Froyd]

On Tue, Feb 23, 2010 at 03:37:16PM -0600, Rob Landley wrote:
> I've been building a powerpc4xx system image, but booting it under g3beige 
> because last I checked qemu doesn't emulate a 4xx processor?  (It has a bamboo 
> board, but only lets you use it under kvm...)

This part is easy to answer: QEMU doesn't emulate the BookE bits to make
qemu-system-ppc work properly.  But if you're running under KVM, then
(the lack of) QEMU's BookE bits don't come into the picture.

-Nathan