Support an inter-vm shared memory device that maps a shared-memory object
as a PCI device in the guest. This patch also supports interrupts between
guest by communicating over a unix domain socket. This patch applies to the
qemu-kvm repository.
This device now creates a qemu character device and sends 1-bytes messages to
trigger interrupts. Writes are trigger by writing to the "Doorbell" register
on the shared memory PCI device. The lower 8-bits of the value written to this
register are sent as the 1-byte message so different meanings of interrupts can
be supported.
Interrupts are supported between multiple VMs by using a shared memory server
-ivshmem<size in MB>,[unix:<path>][file]
Interrupts can also be used between host and guest as well by implementing a
listener on the host that talks to shared memory server. The shared memory
server passes file descriptors for the shared memory object and eventfds (our
interrupt mechanism) to the respective qemu instances.