------- Comment From [email protected] 2017-03-06 15:21 EDT-------
(In reply to comment #10)
> > Next, I will look at ubuntu-1704 kernel to figure out which commits are
> > required for this to work.
>
> commit 3dbbaf200f532e01e56168b8339f2981f2cb1d67
> Author: Michael Roth <[email protected]>
> Date:   Mon Feb 20 19:12:18 2017 -0600
>
>     powerpc/pseries: Advertise Hot Plug Event support to firmware
>
>     With the inclusion of commit 333f7b76865b ("powerpc/pseries: Implement
>     indexed-count hotplug memory add") and commit 753843471cbb
>     ("powerpc/pseries: Implement indexed-count hotplug memory remove"), we
>     now have complete handling of the RTAS hotplug event format as described
>     by PAPR via ACR "PAPR Changes for Hotplug RTAS Events".
>
>     This capability is indicated by byte 6, bit 2 (5 in IBM numbering) of
>     architecture option vector 5, and allows for greater control over
>     cpu/memory/pci hot plug/unplug operations.
>
>     Existing pseries kernels will utilize this capability based on the
>     existence of the /event-sources/hot-plug-events DT property, so we
>     only need to advertise it via CAS and do not need a corresponding
>     FW_FEATURE_* value to test for.
>
>     Signed-off-by: Michael Roth <[email protected]>
>     Signed-off-by: Michael Ellerman <[email protected]>
>
> The above commit is missing from 1704 kernel. This commit is needed to fix
> the issue seen in this bugzilla. More importantly, this commit is needed for
> memory unplug support.
>
> Vipin - Can you follow up with Ubuntu and get this patch included into 1704
> kernel ?

Because QEMU will also use the flag set by the above patch as an
indicator for memory unplug support, as well as count+indexed-based
memory hotplug support, I think we'd also want to include the patches
required for those memory hotplug operations as well. Otherwise memory
hotplug/unplug may not function correctly with the patch applied.

The following list of commits should do it (from most recent to oldest
commit):

3dbbaf2 powerpc/pseries: Advertise Hot Plug Event support to firmware
943db62 powerpc/pseries: Revert 'Auto-online hotplugged memory'
7538434 powerpc/pseries: Implement indexed-count hotplug memory remove
333f7b7 powerpc/pseries: Implement indexed-count hotplug memory add
673bc43 powerpc/pseries: Report DLPAR capabilities

The "Report DLPAR capabilities" one is optional for KVM, but may be
needed in order for PowerVM guests to use the in-kernel mechanisms for
cpu/memory.

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https://bugs.launchpad.net/bugs/1670315

Title:
  Ubuntu 17.04: Guest does not reflect all the cpus hotplugged

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