Re: [PATCH 2/2] x86: implement multiple queues for smp function call IPIs

[Andi Kleen <andi@firstfloor.org>]

> Before going into all the fine details an trying our luck in tip/master 
> QA, i'm a bit worried about hw compatibility in general though. APICs 
> have been flaky since the beginnings of times. We had erratas in the 
> area of local timer IRQs(IPIs) overlapping with IPIs, etc. - so i'd not 
> bet the farm on all APICs being able to handle a _lot_ more overlapped 
> inter-CPU IPIs than we do currently. (which basically was just three of 
> them until now, and now four with the new SMP cross-call IPIs)

At least on 64bit systems this configuration has been already tested
for years with the 8 vector TLB flush. I am not aware
of any problems caused by it. Using them on them should be fine.

So your cautious approach would only be potentially useful on older 32bit only
systems.

-Andi