Re: [Xen-devel] [PATCH] Fix cpumap setting before passing to XEN

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Wei Liu writes ("Re: [Xen-devel] [PATCH] Fix cpumap setting before passing to 
XEN"):
> So what is the conclusion of this discussion so far? I admit I'm a bit
> lost here.

Undoubtedly:

* That "xm ..." generates the reported error is definitely a bug.

* "xm" exists only in versions of Xen now no longer supported
  upstream.

* Applying the proposed patch to libxc in upstream supported versions
  of Xen will not fix "xm" for users like Zhenzhong Duan.


There are two possible views about the nature of the bug:

1. It is xm's fault for passing an invalid cpumap.

2. It is python xc's fault for failing to tolerate a cpumap with
   bits set which do not correspond to actual cpus.

In the case 1., the xm python code needs to be changed.  But there is
nothing for upstream to do because none of our supported trees contain
this code any more.

In the case 2., the in-tree python xc code should be changed.


I am somewhat reluctant to go down the path implied by case 2, because
we don't know what collateral damage there may be.  OTOH the proposed
patch is one which tolerates a wider range of inputs, which is fairly
safe.

I think that the behaviour of libxl (which has to provide a C API,
rather than a python one) is a poor guide to the best behaviour for
python xc.


So I still don't have a clear view about whether the patch should be
applied.  (I think it clearly shouldn't be backported.)

Ian.

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