[Qemu-devel] [PATCH v6 0/3] s390: Support for Hotplug of Standby Memory

[Matthew Rosato]

This patchset adds support in s390 for a pool of standby memory,
which can be set online/offline by the guest (ie, via chmem).
The standby pool of memory is allocated as the difference between 
the initial memory setting and the maxmem setting.
As part of this work, additional results are provided for the 
Read SCP Information SCLP, and new implentation is added for the 
Read Storage Element Information, Attach Storage Element, 
Assign Storage and Unassign Storage SCLPs, which enables the s390 
guest to manipulate the standby memory pool.

This patchset is based on work originally done by Jeng-Fang (Nick)
Wang.

Sample qemu command snippet:

qemu -machine s390-ccw-virtio  -m 1024M,maxmem=2048M,slots=32 -enable-kvm

This will allocate 1024M of active memory, and another 1024M 
of standby memory.  Example output from s390-tools lsmem:
=============================================================================
0x0000000000000000-0x000000000fffffff        256  online   no         0-127
0x0000000010000000-0x000000001fffffff        256  online   yes        128-255
0x0000000020000000-0x000000003fffffff        512  online   no         256-511
0x0000000040000000-0x000000007fffffff       1024  offline  -          512-1023

Memory device size  : 2 MB
Memory block size   : 256 MB
Total online memory : 1024 MB
Total offline memory: 1024 MB


The guest can dynamically enable part or all of the standby pool 
via the s390-tools chmem, for example:

chmem -e 512M

And can attempt to dynamically disable:

chmem -d 512M


Changes for v6:
 * Fix in sclp.h - DeviceState parent --> SysBusDevice parent 
   in struct sclpMemoryHotplugDev.
 * Fix in assign_storage - int this_subregion_size, should 
   be uint64_t.
 * Added information on how to test in the cover letter.  

Changes for v5:
 * Since ACPI memory hotplug is now in, removed Igor's patches 
   from this set.
 * Updated sclp.c to use object_resolve_path() instead of 
   object_property_find().

Changes for v4:
 * Remove initialization code from get_sclp_memory_hotplug_dev()
   and place in its own function, init_sclp_memory_hotplug_dev().
 * Add hit to qemu-options.hx to note the fact that the memory 
   size specified via -m might be forced to a boundary.
 * Account for the legacy s390 machine, which does not support 
   memory hotplug.
 * Fix a bug in sclp.c - Change memory hotplug device parent to 
   sysbus.
 * Pulled latest version of Igor's patch. 

Matthew Rosato (3):
  sclp-s390: Add device to manage s390 memory hotplug
  virtio-ccw: Include standby memory when calculating storage increment
  sclp-s390: Add memory hotplug SCLPs

 hw/s390x/s390-virtio-ccw.c |   46 +++++--
 hw/s390x/sclp.c            |  289 +++++++++++++++++++++++++++++++++++++++++++-
 include/hw/s390x/sclp.h    |   20 +++
 qemu-options.hx            |    3 +-
 target-s390x/cpu.h         |   18 +++
 target-s390x/kvm.c         |    5 +
 6 files changed, 366 insertions(+), 15 deletions(-)

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1.7.9.5