[libvirt] RHBZ 1013045: Crash on xen domain startup

[Daniel P. Berrange]

On Thu, Oct 31, 2013 at 06:50:57PM -0600, Jim Fehlig wrote:
> Jeremy Fitzhardinge wrote:
> > On 10/30/2013 12:04 PM, Eric Blake wrote:
> >   
> >> On 10/30/2013 01:00 PM, Jeremy Fitzhardinge wrote:
> >>     
> >>> On 10/30/2013 11:37 AM, Eric Blake wrote:
> >>>       
> >>>> On 10/30/2013 11:38 AM, Jeremy Fitzhardinge wrote:
> >>>>         
> >>>>>     libxl: fix dubious cpumask handling in libxlDomainSetVcpuAffinities
> >>>>>
> >>>>>     Rather than casting the virBitmap pointer to uint8_t* and then
> >>>>>           
> > using
> >   
> >>>>>     the structure contents as a byte array, use the virBitmap API to
> >>>>> determine
> >>>>>     the bitmap size and test each bit.
> >>>>>           
> >>>> Hmm, we already have virBitmapToData for converting from a virBitmap to
> >>>> a uint8_t; using that would be much faster for populating cpumap than
> >>>> doing a per-bit iteration over cpumask.
> >>>>         
> >>> I looked at that, but I couldn't see it being any more efficient given
> >>> that we're typically talking about a small number of (v)CPUs.
> >>>       
> >> Efficiency isn't my concern.  Maintainability is.  It's better to reuse
> >> existing functions instead of risking open-coding it wrong.  We have a
> >> testsuite over our existing functions, but not over your open-coding.
> >>     
> >
> > Well, that was also a consideration, but using virBitmapToData would be
> > more complex. The same loop would exist, but I'd also have to manage
> > freeing the array.  So this seems like the better of the two approaches.
> >   
> 
> What is the consensus here? It would be nice to get this pushed for
> 1.1.4 since it fixes a libvirtd segfault. I prefer Jeremy's approach of
> less memory management.
> 

Absolutely want this in 1.1.4. Personally I think Jeremy's patch
is fine.

Daniel
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