Re: [Qemu-devel] [Qemu-ppc] [PATCH 00/77] ppc: Add "native" POWER8 platform

[Stewart Smith]

Cédric Le Goater <address@hidden> writes:
> On 11/28/2015 08:59 AM, Benjamin Herrenschmidt wrote:
>> On Fri, 2015-11-27 at 11:21 +0100, Alexander Graf wrote:
>>>
>>> How does real hardware store petitboot? If it's flash, you could pass it
>>> in using -pflash and thus model things even more closely and allow users
>>> to just take the ROM image as is.
>> 
>> It is a flash image, we could use an Open Power machine flash image "as-is"
>> provided we taught qemu to extract skiboot (aka OPAL) from it.
>
> Couldn't we add an offset argument to load_image_targphys() or make that 
> an extra routine ? If so, we could then load directly from an openpower 
> pnor file. 
>
> I gave it a quick (and dirty) try and a powernv guest runs fine up to 
> petitboot with just :
>
>       qemu-system-ppc64 -m 2G -M powernv -bios  
> ~/work/open-power/images/palmetto.pnor -nographic -nodefaults -serial stdio
>
> The pnor file is compiled from github. The patch is below (without the dirty
> cut and paste I did in loader.c). The offset for the PAYLOAD and BOOTKERNEL
> partitions are hard coded but I guess we don't need to read the flash 
> partition
> table in qemu, not yet.

One downside to this is that if we don't fall back to being able to load
skiboot.lid it becomes more annoying to boot a gcov enabled skiboot as
typical PNOR layout only gives 1MB for skiboot, and gcov builds bloat
that a *lot*.

We probably don't want NVRAM writes going back to a single system wide
PNOR image too, so while using pnor file is great for simulating what
hardware does, may not work as the solution for long term model.