xc_tbuf_set_cpu_mask & xentrace & cpu_mask

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Hey George,

I recently got my hands on a machine with 240CPUS (ugh!) and wanted to play
a bit on figuring out what is happening with certain guests if I partition
it the box in nice per-socket pools.

While I was setting this up I started looking at xentrace and figuring out
what to set the cpu_mask and then I realized it is limited to 64 cpus. Or
at least that is my understanding (with not enough sleep - maybe I am
missing something?).

I see this xc_tbuf_set_cpu_mask which accepts a 32-bit mask and in the
code I see:

sysctl.u.tbuf_op.cpu_mask.nr_bits = sizeof(bytemap) * 8;

where bytemap is a uint8. That all reads to me as a 64-bit mask (thought
we only pass in a 32-bit mask?). Seems like two bugs there.

The hypervisor part is OK - it does the right thing.

Am I reading the code right? And if so, do you have some patches in
your backlog that had addressed this by any chance?

Thanks.