Messages in this thread | | | Date | Thu, 26 Feb 2015 14:02:38 +0100 | From | Paolo Bonzini <> | Subject | Re: [PATCH 0/2] powerpc/kvm: Enable running guests on RT Linux |
| |
On 24/02/2015 00:27, Scott Wood wrote: > This isn't a host PIC driver. It's guest PIC emulation, some of which > is indeed not suitable for a rawlock (in particular, openpic_update_irq > which loops on the number of vcpus, with a loop body that calls > IRQ_check() which loops over all pending IRQs).
The question is what behavior is wanted of code that isn't quite RT-ready. What is preferred, bugs or bad latency?
If the answer is bad latency (which can be avoided simply by not running KVM on a RT kernel in production), patch 1 can be applied. If the answer is bugs, patch 1 is not upstream material.
I myself prefer to have bad latency; if something takes a spinlock in atomic context, that spinlock should be raw. If it hurts (latency), don't do it (use the affected code).
Paolo
> The vcpu limits are a > temporary bandaid to avoid the worst latencies, but I'm still skeptical > about this being upstream material.
| |