Re: [Xen-devel] [PATCH v3 ]libxl: allow to set more than 31 vcpus

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2012-06-01 at 11:47 +0100, Dario Faggioli wrote:
> On Fri, 2012-06-01 at 11:38 +0100, Ian Campbell wrote: 
> > > Anyway, I just tried 25 and 33 and 65, and creation of the domain worked
> > > without raising any errors! Then I double-checked, and saw that, in the
> > > 'above 16' cases, Xen deliberately paused a lot of VCPUs. Also, if I log
> > > into the guest /proc/cpuinfo reports only CPUs 0 and 32 (and 64 in the
> > > 65 VCPUs case).
> > 
> > All 64 online?
> > 
> I see all of them from the host (xl vcpu-list) but a kind of random
> number of them from the guest...

Which is probably the overflow I mentioned giving you a random set of
online cpus after #32...

> > libxl__build_post is also probably buggy with max_vcpus >
> > nr-bits-in(curr_vcpus) and from the looks of it it just overflows off
> > the end(!), which is also fixed here...
> > 
> What I can do is trying again with the patch applied, and if it still
> behaves weird I'll go seeing what might be still missing.
> 
> > > "max. number of cpus supported by hypervisor" to be different from the
> > > actual number of physical processors, and I was sort-of mislead by the
> > > machine I use to test Xen every day (where that is actually happening!).
> > > If it is not like that, I guess I can agree with you on this change.
> > 
> > It's certainly supposed to be "get max. number of physical cpus", quite
> > how that relates to the actual number of physical cpus I'm not sure.
> > 
> > It's definitely not something to do with virtual cpus (for which there
> > is a limit, but not this one...)
> > 
> Ok, with that "physical" you're putting there, I see and agree it could
> be useful untie it from the "virtual world". :-)

Is that an ACK for this and/or the previous patch?

> 
> Thanks and Regards,
> Dario
> 



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