[Qemu-devel] [RFC PATCH v1 0/4] Handle memory hotplug errors from guest OS.

[Tang Chen]

When doing memory hotplug, QEmu is not aware of guest OS error when hotplugging
memory devices. Even if guest OS failed to hot-add memory, the pc-dimm
device will be added to QEmu. Even if guest OS failed to hot-remove memory,
QEmu will remove the pc-dimm device.

An example is: for a Linux guest, the Linux kernel limited that the size of
hot-added memory should be mutiple of memory section (128MB by default).
If we add 130MB memory, the Linux kernel won't add it. We are not able
to handle the size check in QEmu commmand line because different OS may
have different limits.

And also, QEmu outputs nothing but guest OS failed to hot-add memory will
confuse users. We should at least report an error.

So, we should report the error to users, and cancel the memory hotplug
progress in QEmu.

QEmu thread sends a SCI to guest OS and return immediately. The vcpu thread
will emulate ACPI hardware operations. So this patch-set introduces a wait 
condition variable to synchronize these two threads.

Tang Chen (4):
  Use macro to define ACPI notification event.
  Add event handling for memory device insertion.
  Introduce wait condition to catch guest OS memory hotplug error.
  Handle memory hotplug error from guest OS in QEmu.

 hw/acpi/memory_hotplug.c | 146 +++++++++++++++++++++++++++++++++++++++++++++--
 include/hw/acpi/acpi.h   |  15 ++++-
 2 files changed, 153 insertions(+), 8 deletions(-)

-- 
1.8.4.2