On Fri, 10 Jul 2015 17:35:08 +0200 Eduardo Otubo <eduardo.ot...@profitbricks.com> wrote:
> > > > > 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? build QEMU with tracing enabled and you can use it to see what's going on in QEMU<->guest ACPI interface. $grep mhp trace-events mhp_acpi_invalid_slot_selected(uint32_t slot) "0x%"PRIx32 mhp_acpi_ejecting_invalid_slot(uint32_t slot) "0x%"PRIx32 mhp_acpi_read_addr_lo(uint32_t slot, uint32_t addr) "slot[0x%"PRIx32"] addr lo: 0x%"PRIx32 mhp_acpi_read_addr_hi(uint32_t slot, uint32_t addr) "slot[0x%"PRIx32"] addr hi: 0x%"PRIx32 mhp_acpi_read_size_lo(uint32_t slot, uint32_t size) "slot[0x%"PRIx32"] size lo: 0x%"PRIx32 mhp_acpi_read_size_hi(uint32_t slot, uint32_t size) "slot[0x%"PRIx32"] size hi: 0x%"PRIx32 mhp_acpi_read_pxm(uint32_t slot, uint32_t pxm) "slot[0x%"PRIx32"] proximity: 0x%"PRIx32 mhp_acpi_read_flags(uint32_t slot, uint32_t flags) "slot[0x%"PRIx32"] flags: 0x%"PRIx32 mhp_acpi_write_slot(uint32_t slot) "set active slot: 0x%"PRIx32 mhp_acpi_write_ost_ev(uint32_t slot, uint32_t ev) "slot[0x%"PRIx32"] OST EVENT: 0x%"PRIx32 mhp_acpi_write_ost_status(uint32_t slot, uint32_t st) "slot[0x%"PRIx32"] OST STATUS: 0x%"PRIx32 mhp_acpi_clear_insert_evt(uint32_t slot) "slot[0x%"PRIx32"] clear insert event" mhp_acpi_clear_remove_evt(uint32_t slot) "slot[0x%"PRIx32"] clear remove event" mhp_acpi_pc_dimm_deleted(uint32_t slot) "slot[0x%"PRIx32"] pc-dimm deleted" mhp_acpi_pc_dimm_delete_failed(uint32_t slot) "slot[0x%"PRIx32"] pc-dimm delete failed" mhp_pc_dimm_assigned_slot(int slot) "0x%d" mhp_pc_dimm_assigned_address(uint64_t addr) "0x%"PRIx64 events of interest for you may be *_ost_* you can check hw/acpi/memory_hotplug.c for events meaning You also might need to enable ACPI debugging in guest to see what's happening on guest side if there is no *pc_dimm_deleted event in the trace. > > > > > > > > > > > > 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! :) >
