Re: [Xen-devel] [Patch] use full-size cpumask for vcpu-pin

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Keir Fraser writes ("Re: [Xen-devel] [Patch] use full-size cpumask for 
vcpu-pin"):
> Actually, now I look at it, I have to NACK the patch. Sorry I didn't look
> closely enough earlier. I think the bug can be addressed without any
> hypervisor changes: when vcpu-pinning, the tools can quite correctly pass a
> cpumask to Xen just big enough to express just the CPUs in the new affinity
> set. If the resulting mask is too narrow to address all CPUs in the system,
> then Xen will pad it out with zeroes. If the resulting mask is too wide, Xen
> will simply truncate it. All this is done silently at the time of the
> setvcpuaffinity hypercall.

The difficulty is, as I understand it, how to express the mask "all
CPUs present and future".  Since the number of pcpus may be very
large.  The tools presumably shouldn't pass a kilobyte of 0xff :-).

Ian.

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