Re: [PATCH 2/2] Xen ACPI memory hotplug

Erlon Cruz
Mon, 11 Mar 2013 13:17:27 -0000

On Mon, Mar 11, 2013 at 5:14 AM, Liu, Jinsong <jinsong.liu@intel.com>
wrote:

> Erlon Cruz wrote:
> > [snip]
> >> +config XEN_ACPI_HOTPLUG_MEMORY
> >> +    tristate "Xen ACPI memory hotplug"
> >> +    depends on XEN_DOM0 && XEN_STUB && ACPI
> >> +    default n
> >> +    help
> >> +      This is Xen ACPI memory hotplug.
> >> +
> >> +      Currently Xen only support ACPI memory hot-add. If you want
> >> +      to hot-add memory at runtime (the hot-added memory cannot
be
> >> +      removed until machine stop), select Y/M here, otherwise
select N.
> >
> > I''m wondering if the memory removal is not implemented
because of the
> > same complication QEMU developers are having. To find a way to keep
> > track of the references to to memory to be removed (e.g in DMA block
> > operations). Did you had this issue?
> >
>
> Sorry for late reply.
>
>
Hi Liu, thanks for replying, no problem.

Per my understanding, currently to hot-remove memory is more
complicated
> than to hot-add memory, not only bz of complication of QEMU, but hard to
> reclaim data structure os/vmm already alloc and occupy. Maybe it would
> become simpler w/ some h/w assist tech next generation.
>
>
Hmm, it makes sense. I read a few discussions about the issue on QEMU list
but didn''t see any clear solution for the problem.


> Thanks,
> Jinsong


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