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

Liu, Jinsong
Mon, 11 Mar 2013 08:14:50 -0000

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.

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.

Thanks,
Jinsong