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[Qemu-devel] [PATCH v4 0/7] Fix QEMU crash during memory hotplug with vh

From: Igor Mammedov
Subject: [Qemu-devel] [PATCH v4 0/7] Fix QEMU crash during memory hotplug with vhost=on
Date: Thu, 9 Jul 2015 13:47:17 +0200

   * drop patch extending memory_region_subregion_add()
     with error argument
   * and add memory_region_add_subregion_to_hva() API instead
   * add madvise(DONTNEED) when returning range to HVA container
   * fixed(work-arouned) unmapping issues,
     now memory subsytem keeps track of HVA mapped
     regions and doesn't allow to map a new region
     at address where previos has benn mapped until
     previous region is gone
   * fixed offset calculations in memory_region_find_hva_range()
     in 2/8
   * redone MemorySection folding into HVA range for VHOST,
     now compacted memory map is temporary and passed only to vhost
     backend and doesn't touch original memory map used by QEMU
   * take into account Paolo's review comments
     * do not overload ram_addr
     * ifdef linux specific code
   * reseve HVA using API from exec.c instead of calling
     mmap() dircely from memory.c
   * support unmapping of HVA remapped region

When more than ~50 pc-dimm devices are hotplugged with
vhost enabled, QEMU will assert in vhost vhost_commit()
due to backend refusing to accept too many memory ranges.

Series introduces Reserved HVA MemoryRegion container
where to all hotplugged memory is remapped and passes
the single container range to vhost instead of multiple
memory ranges for each hotlugged pc-dimm device.

It's an alternative approach to increasing backend supported
memory regions limit. 

Tested it a bit more, so now
 - migration from current master to patched version seems to work
 - memory is returned to host after device_del+object_del sequence,
   but I can't bet if cgroups won't charge it.

git branch for testing:

Igor Mammedov (7):
  memory: get rid of memory_region_destructor_ram_from_ptr()
  memory: introduce MemoryRegion container with reserved HVA range
  pc: reserve hotpluggable memory range with
  pc: fix QEMU crashing when more than ~50 memory hotplugged
  exec: make sure that RAMBlock descriptor won't be leaked
  exec: add qemu_ram_unmap_hva() API for unmapping memory from HVA area
  memory: add support for deleting HVA mapped MemoryRegion

 exec.c                    |  71 +++++++++++++++++++----------
 hw/i386/pc.c              |   4 +-
 hw/mem/pc-dimm.c          |   6 ++-
 hw/virtio/vhost.c         |  47 ++++++++++++++++++--
 include/exec/cpu-common.h |   3 ++
 include/exec/memory.h     |  67 +++++++++++++++++++++++++++-
 include/exec/ram_addr.h   |   1 -
 include/hw/virtio/vhost.h |   1 +
 memory.c                  | 111 +++++++++++++++++++++++++++++++++++++++++++---
 9 files changed, 272 insertions(+), 39 deletions(-)


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