On 08/10/2017 07:54 AM, David Gibson wrote:
On Thu, Aug 10, 2017 at 02:46:00PM +1000, Benjamin Herrenschmidt wrote:
quoted
On Thu, 2017-08-10 at 14:28 +1000, David Gibson wrote:
quoted
Also, will POWER9 always have doorbells? In which case you could
reduce it to 3 options.
The problem with doorbells on POWER9 guests is that they may have
to trap and be emulated by the hypervisor, since the guest threads
on P9 don't have to match the HW threads of the core.
Thus it's quite possible that using XIVE for IPIs is actually faster
than doorbells in that case.
Ok, well unless there's a compelling reason to use doorbells you can
instead make it 3 cases with POWER9 never using doorbells.
yes I suppose we could improve things for XIVE. For XICS, there are
another 3 backends behind icp_ops->cause_ipi. I need to take a look.
Thanks,
C.