Hi, [...] >> > > >> > > 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: >> > > can't we simply track this(MemoryRegion) usage by ref-count? > e.g. > every time mr used, inc ref-count, then dec it when unused > even for cpu_physical_memory_map and other potential users. >
yes, that's the idea the patchset below try to implement, but last time I checked this was not upstreamed. I will take a closer look next week. >> > > 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. - Vasilis
