[PATCH] powerpc/pseries: Use doorbells even if XIVE is available

[Cédric Le Goater]

[ ...  ]

>>> An option vector (or dt-cpu-ftrs) could be defined to disable msgsndp
>>> to get KVM performance back.
> 
> An option vector would require a PAPR change. Unless the architecture 
> reserves some bits for the implementation, but I don't think so. Same
> for CAS.
> 
>> Qemu/KVM populates /proc/device-tree/hypervisor, so we *could* look at
>> that. Though adding PowerVM/KVM specific hacks is obviously a very
>> slippery slope.
> 
> QEMU could advertise a property "emulated-msgsndp", or something similar, 
> which would be interpreted by Linux as a CPU feature and taken into account 
> when doing the IPIs.

This is really a PowerVM optimization. 

> The CPU setup for XIVE needs a cleanup also. There is no need to allocate
> interrupts for IPIs anymore in that case.

We need to keep these for the other cores. The XIVE layer is unchanged.
 
C.