Re: [Xen-ia64-devel] [PATCH] Port of mini-os to ia64

[Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxxxxxxx>]

Hi Alex,

Am Montag, 12. Februar 2007 16:28 schrieb Alex Williamson:
>...
> Hi Dietmar,
>
>    Yes, I think we would want a mini-os port in the source.  Skimming
> through the patch, my first impression is that this seems more like a PV
> port of FreeBSD than a truly "minimal" OS.  If we're designing an OS to
> run only in PV mode on Xen/ia64, can we remove some of the ia64 bare
> metal components?  Perhaps ripping out some PAL/SAL/EFI/ACPI specific
> layers?  And if we do need those components in a mini-os, would it make
> more sense to leverage them from Linux than FreeBSD?  Maybe some
> discussion of your design decisions would help me understand better.
> Thanks,
>
>       Alex

my main goal at the beginning  was to fit in the existing x86-mini-os 
structure with as few changes as possible.
The PAL/SAL/EFI comes in when I tried the timer stuff. I found, that xen-ia64 
doesn't support the wallclock time stuff, so I had a look at  PAL/SAL/EFI to 
get the entrypoints to the SAL and PAL functions (for processor and board 
clock ticks, ratios and efi time). If there is another way to handle the 
timing stuff, we can remove this.
The ACPI  stuff was only a try to use more than one vcpu and to see how the 
firmware emulation works. This can be removed for a mono-cpu mini-os.
I used parts from FreeBSD because I had some experience with ia64-FreeBSD.
The other side is that mini-os maybe the base for a proof of concept, 
including the big endian stuff (I wrote earlier about this on the list), so 
there is a legal reason (no usage of GPL code).
As you can see, there are no special design decisions, it's mostly driven by 
practical considerations.
Thanks.

Dietmar.

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