Re: [Xen-devel] [PATCH] Bug #327 xentop/libxenstat vcpu fix

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 16 Oct 2005, at 01:11, Daniel Stekloff wrote:

> Ok.. so xm top/xentop is no longer broken - provided you don't care 
> about out
> of order vcpus.
This doesn't make sense..... see below.

> xm vcpu-list is broken.
Yes, Ewan is working on a fix for this.

> xm vcpu-enable will only enable vcpus in order.  I can't, for 
> instance, enable
> vcpu 3 if vcpu 2 isn't enabled. xm vcpu-enable silently fails.
This is currently supposed to work. It looks as though the 'xm 
vcpu-enable/disable' commands are still not 100% robust. :-( Longer 
term, allowing an admin to take down specific vcpus probably isn't all 
that useful, so we may simplify the xm interface.
> Do we no longer have or care about dicontiguous online maps? Or, do 
> the tools
> just need to catch up with your changes?
Although we don't care about exposing them via vcpu-enable/disable, I 
think we ought to handle them. A user logged into domU can still take 
down non-contiguous VCPUs, even if that functionality isn't exported 
via the xm interface.
> I'm curious because xentop just takes the number of vcpus from 
> domaininfo and
> calls GETVCPUCONTEXT starting with 0 and going until num-1. I just 
> tried this
> on a 4 vcpu dom. I disabled vcpus 1 and 2, leaving 0 and 3 active. 
> xentop
> worked fine but reported those vcpus as 0 and 1. GETVCPUCONTEXT 
> returned the
> as 0 and 1. Is this the way you want it to work?
That is definitely not how GETVCPUCONTEXT works. It won't renumber 
vcpus under your feet  -- if you ask for vcpu3 then it is vcpu3's 
information that you will get.
One thing to bear in mind: GETVCPUCONTEXT will return info even about 
vcpus that are not currently online. To check for online status you 
need to use GETVCPUINFO and check the online field that is returned.
Perhaps you iterated from 0 to info.n_vcpu-1? The count from 
GETDOMAININFO only counts online vcpus, but doesn;t tell you which 
vcpus are online. We could also add a count 'max_vcpu' or easier: just 
iterate 0 to MAX_VIRT_CPU-1.
 -- Keir


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