Hot-resizing of Windows VMs via Hyper-V Dynamic Memory Protocol
summary
A QEMU hv-balloon driver implements the Hyper-V Dynamic Memory protocol to hot-add, hot-remove and balloon Windows VM RAM at single-page granularity; an MVP works on x86 Windows Server and uses vmbus despite undocumented protocol details. Kernel-side memslot scalability changes land upstream (kernel 5.17) increasing slots to 32k memslots, and experiments show roughly 3x faster than virtio-balloon for releases of large-range removals, though reboot/NUMA handling and further integration remain incomplete.
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