> > > > Yes, you're right. The reason is surely because dimm1 wasn't deleted > > > > -- and I think I didn't make my point very clear -- my question was > > > > more about: Is there any reason for dimm1 not being deleted? The > > > > reason why I tested with the guest OS fully running and on GRUB is > > > > because I guessed the guest OS was using this memory and couldn't be > > > > deallocated. If that's the case, and qemu did a best effort to remove > > > > and couldn't because guest was using it, then Ok, I just need to > > > > adapt my tests. Other than that perhaps I hit a bug. > > > Guest OS has to: > > > 1. support memory hot remove > > > > How do I know if guest OS supports memory hot remove? I'm testing on > > Debian 8 with kernel 4.1. I start qemu with "-m 2G,slots=32,maxmem=8G". > kernel should be compiled with memory remove options
Double checked that and yes, my guest kernel has memory hotplug support. > > Also memory removal is allowed to fail if guest kernel is not able > to offline corresponding memory sections but it probably should notify > QEMU via ACPI about failure. How can I check this notification? > > > > > > > 2. eject memory device using ACPI _EJ0 method, once it has handled > > > removal request, provided it is able to free corresponding memory pages > > > See docs they should have flows described for success and failure case. > > > > When I issue the command "device_del dimm1" I see no output on dmesg on > > the guest OS. I guess this is a sign that perhaps the guest does not > > support it? > > > > From the (very nice) diagram I found at docs/specs/acpi_mem_hotplug.txt, > > Qemu QMP should output some sort of failure if Guest OS fails to > > process ejection right? The only information I see is: > you need to use query-acpi-ospm-status command to see slot status. Yep, this command outputs that the dimm is still there, no news :/ > > > > > (qemu) device_del dimm1 > > device_del dimm1 > > > > (qemu) info memory-devices > > info memory-devices > > Memory device [dimm]: "dimm1" > > addr: 0x100000000 > > slot: 0 > > node: 0 > > size: 1073741824 > > memdev: /objects/mem1 > > hotplugged: true > > hotpluggable: true > > > > (qemu) info memdev > > info memdev > > memory backend: 0 > > size: 1073741824 > > merge: true > > dump: true > > prealloc: false > > policy: default > > host nodes: > > > > How was the environment when you tested this feature? > Most likely I've used RHEL7.1 as guest with latest systemd > which onlines hotplugged memory automatically on hotplug. I tried with Ubuntu 15.04, latest kernel 4.2 and systemd, still not working. I'm downloading CentOS-7, I'll setup with systemd and proper kernel configuration. I'll let you know the results. Thanks a lot for the help so far! :) -- Eduardo Otubo ProfitBricks GmbH
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