Hi, On Tue, Mar 19, 2013 at 03:28:38PM +0800, li guang 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, > > it seems it mostly up to the user who want to hot-(un)plug, > if user want to un-plug a memory which is kernel's main memory, kernel > will always run on it(never stop) unless power off. > and if guest stops, all DIMMs should be safe to hot-remove, > or else we should do something to let user can unlock all reference.
it's not only the guest-side that needs to stop using it, we need to make sure that the qemu block layer is also not using the memory region anymore. See the 2 links below for discussion: > > 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. > > thanks, - Vasilis
