Re: Memory-hotplug support for x86_64 domUs?

[Jeremy Fitzhardinge <jeremy@goop.org>]

Radhakrishnan, Prashanth wrote:
> Hi,
>
> I wanted to know if the following would work:
> - memory-hotplug on x86_64 domUs
> - memory-hotplug + ballooning interplay (e.g.
> http://lkml.org/lkml/2008/4/3/449), again on x86_64 domUs
>
> For starts, if I read the Xen linux src (at
> http://xenbits.xensource.com/linux-2.6.18-xen.hg) right, it says that
> SPARSEMEM cannot be enabled with X86_64_XEN. Is that right?
>   

No, sparsemem is supported in pvops Xen kernels (both 32 and 64 bit).  
But it isn't very useful at present.

I have some patches to allow balloon expansion by using memory hotplug 
to add new memory to the system.  But unfortunately it requires some 
changes to the memory hotplug subsystem, and last time I posted them we 
(the memory hotplug maintainers and I) failed to converge on a mutually 
acceptable set of patches.  I put it aside to work on some higher value 
things (x86-64 support, mainly), and it's been sitting in the TODO state 
since.

    J