Re: [PATCH] powerpc/xive: fix the fuzz value in xive_pick_irq_target()

On 08/03/2017 01:52 PM, Benjamin Herrenschmidt wrote:

On Thu, 2017-08-03 at 19:52 +1000, Michael Ellerman wrote:

quoted

What if num is 0?

Which it would be in the fallback case, if the affinity mask is empty,
AFAICS.

How can the mask be empty though ? But yes, as I noted there is a
problem if the value is 0. Not sure what to do if we are given an empty
mask though.

I am seeing different problems. 

The fuzz value was one but that was due to the fact that the spapr 
backend did not set the chip_id of the xive_irq_data. I should have 
fix that now. But in some other situations, the weight of the 
'affinity' mask is 2048 (and 'nr_cpu_ids') and that also breaks 
the 'first' calculation. 

I am currently tracking this with the xive support for spapr. I will 
send a fix with the patchset.

Thanks,

C.