Re: [Qemu-devel] Enablig DLPAR capacity on QEMU pSeries

[Alexander Graf]

On 09/12/2012 04:54 PM, Erlon Cruz wrote:
> Hi all,
>
> We are planning to implement DLPAR capacity on QEMU pSeries. As we

What is DLPAR? Hotplug support?

> lack of experience in the internals of the arch we would like you guys
> to give us some design directions
> and confirm if we going in the right direction. Our first idea is:
>
>      1 - to patch 'spapr.c' so it can dynamically insert/remove basic
> items into the device tree.

What exactly would you like to patch into it? We already do have support 
for dynamic dt creation with the spapr target.

>      2 - create a host side device that will be used with a guest side
> driver to perform guest side operations and communicate changes from
> host to the guest (like DynamicRM does in PowerVM LPARs). We are not

Why not just use hypercalls?

> planning to use powerpc-tools and want to make resource management
> transparent (i.e. no need to run daemons or userspace programs in the
> guest, only this kernel driver).
>      3 - create bindings to support adding/removal  ibmvscsi devices
>      4 - create bindings to support adding/removal  ibmveth devices
>      5 - create bindings to support adding/removal PCI devices
>      6 - create bindings to support adding/removal of memory

This is going to be the hardest part. I don't think QEMU supports memory 
hotplug yet.

>          - Do we need to do this the way PowerVM does? We have tested
> virtio ballooning and it can works with a few endiannes corrections.

I don't know how PowerVM works. But if normal ballooning is all you 
need, you should certainly just enable virtio-balloon.

>      7 - create bindings to support adding/removal  CPUs
>          - is SMP supported already? I tried to run SMP in a x86 host
> and the guest stuck when SMP is enabled

SMP should work just fine, yes. Where exactly does it get stuck?

>          - would be possible to work on this without a P7 baremetal
> machine?

At least for device hotplug, it should be perfectly possible to use an 
old G5 with PR KVM. I haven't gotten around to patch all the pieces of 
the puzzle to make -M pseries work with PR KVM when it's running on top 
of pHyp yet, so that won't work.

> We have a P7 8205-E6B, is that possible to kick PHYP out?

Ben?

> Any ideia on how much effort (time/people) the hole thing would take?
> Any consideration about this is much appreciated :)

Phew. It's hard to tell. Depends heavily on how good your people are :).


Alex