This is the very basic/initial version of virtio-mem. An introduction to
virtio-mem can be found in the Linux kernel driver [1]. While it can be
used in the current state for hotplug of a smaller amount of memory, it
will heavily benefit from resizeable memory regions in the future.
Each virtio-mem device manages a memory region (provided via a memory
backend). After requested by the hypervisor ("requested-size"), the
guest can try to plug/unplug blocks of memory within that region, in order
to reach the requested size. Initially, and after a reboot, all memory is
unplugged (except in special cases - reboot during postcopy).
The guest may only try to plug/unplug blocks of memory within the usable
region size. The usable region size is a little bigger than the
requested size, to give the device driver some flexibility. The usable
region size will only grow, except on reboots or when all memory is
requested to get unplugged. The guest can never plug more memory than
requested. Unplugged memory will get zapped/discarded, similar to in a
balloon device.
The block size is variable, however, it is always chosen in a way such that
THP splits are avoided (e.g., 2MB). The state of each block
(plugged/unplugged) is tracked in a bitmap.
As virtio-mem devices (e.g., virtio-mem-pci) will be memory devices, we now
expose "VirtioMEMDeviceInfo" via "query-memory-devices".
+##
+{ 'struct': 'VirtioMEMDeviceInfo',
+ 'data': { '*id': 'str',
+ 'memaddr': 'size',
+ 'requested-size': 'size',
+ 'size': 'size',
+ 'max-size': 'size',
+ 'block-size': 'size',
+ 'node': 'int',
+ 'memdev': 'str'
+ }
+}
+
##
# @MemoryDeviceInfo:
#
# Union containing information about a memory device
#
# nvdimm is included since 2.12. virtio-pmem is included since 4.1.
+# virtio-mem is included since 5.2.