[SeaBIOS] [Qemu-devel] [RFC PATCH v4 00/30] ACPI memory hotplug

[Vasilis Liaskovitis]

Hi,

sorry for the delay.
On Tue, Feb 19, 2013 at 07:39:40PM -0300, Erlon Cruz wrote:
> On Tue, Dec 18, 2012 at 10:41 AM, Vasilis Liaskovitis <
> vasilis.liaskovitis at profitbricks.com> wrote:
> 
> > This is v4 of the ACPI memory hotplug functionality. Only x86_64 target is
> > supported (both i440fx and q35). There are still several issues, but it's
> > been a while since v3 and I wanted to get some more feedback on the current
> > state of the patchseries.
> >
> >
> We are working in memory hotplug functionality on pSeries machine. I'm
> wondering whether and how we can better integrate things. Do you think the
> DIMM abstraction is generic enough to be used in other machine types?

I think the DimmDevice is generic enough but I am open to other suggestions. 

A related issue is that the patchseries uses a DimmBus to hot-add and hot-remove
DimmDevice. Another approach that has been suggested is to use links<> between
DimmDevices and the dram controller device (piix4 or mch for pc and q35-pc
machines respectively). This would be more similar to the CPUState/qom
patches - see Andreas Färber's earlier reply to this thread.

I think we should get some consensus from the community/maintainers before we
continue to integrate. 

I haven't updated the series for a while, but I can rework if there is a more
clear direction for the community.

Another open issue is reference counting of memoryregions in qemu memory
model. In order to make memory hot-remove operations safe, we need to remove
a memoryregion after all users (e.g. both guest and block layer) have stopped
using it, see discussion at
http://lists.gnu.org/archive/html/qemu-devel/2012-10/msg03986.html. There was a
relevant ibm patchset
https://lists.gnu.org/archive/html/qemu-devel/2012-11/msg02697.html
but it was not merged.

> 
> 
> > Overview:
> >
> > Dimm device layout is modeled with a normal qemu device:
> >
> > "-device dimm,id=name,size=sz,node=pxm,populated=on|off,bus=membus.0"
> >
> >
>  How does this will handle the no-hotplugable memory for example the memory
> passed in '-m' parameter?

The non-hotpluggable initial memory (-m) is currently not modelled at all as a
DimmDevice. We may want to model it though.

thanks,
- Vasilis