1Multi-process QEMU 2================== 3 4This document describes how to configure and use multi-process qemu. 5For the design document refer to docs/devel/qemu-multiprocess. 6 71) Configuration 8---------------- 9 10multi-process is enabled by default for targets that enable KVM 11 12 132) Usage 14-------- 15 16Multi-process QEMU requires an orchestrator to launch. 17 18Following is a description of command-line used to launch mpqemu. 19 20* Orchestrator: 21 22 - The Orchestrator creates a unix socketpair 23 24 - It launches the remote process and passes one of the 25 sockets to it via command-line. 26 27 - It then launches QEMU and specifies the other socket as an option 28 to the Proxy device object 29 30* Remote Process: 31 32 - QEMU can enter remote process mode by using the "remote" machine 33 option. 34 35 - The orchestrator creates a "remote-object" with details about 36 the device and the file descriptor for the device 37 38 - The remaining options are no different from how one launches QEMU with 39 devices. 40 41 - Example command-line for the remote process is as follows: 42 43 /usr/bin/qemu-system-x86_64 \ 44 -machine x-remote \ 45 -device lsi53c895a,id=lsi0 \ 46 -drive id=drive_image2,file=/build/ol7-nvme-test-1.qcow2 \ 47 -device scsi-hd,id=drive2,drive=drive_image2,bus=lsi0.0,scsi-id=0 \ 48 -object x-remote-object,id=robj1,devid=lsi1,fd=4, 49 50* QEMU: 51 52 - Since parts of the RAM are shared between QEMU & remote process, a 53 memory-backend-memfd is required to facilitate this, as follows: 54 55 -object memory-backend-memfd,id=mem,size=2G 56 57 - A "x-pci-proxy-dev" device is created for each of the PCI devices emulated 58 in the remote process. A "socket" sub-option specifies the other end of 59 unix channel created by orchestrator. The "id" sub-option must be specified 60 and should be the same as the "id" specified for the remote PCI device 61 62 - Example commandline for QEMU is as follows: 63 64 -device x-pci-proxy-dev,id=lsi0,socket=3 65