1.. _Multi-process QEMU: 2 3Multi-process QEMU 4================== 5 6This document describes how to configure and use multi-process qemu. 7For the design document refer to docs/devel/qemu-multiprocess. 8 91) Configuration 10---------------- 11 12multi-process is enabled by default for targets that enable KVM 13 14 152) Usage 16-------- 17 18Multi-process QEMU requires an orchestrator to launch. 19 20Following is a description of command-line used to launch mpqemu. 21 22* Orchestrator: 23 24 - The Orchestrator creates a unix socketpair 25 26 - It launches the remote process and passes one of the 27 sockets to it via command-line. 28 29 - It then launches QEMU and specifies the other socket as an option 30 to the Proxy device object 31 32* Remote Process: 33 34 - QEMU can enter remote process mode by using the "remote" machine 35 option. 36 37 - The orchestrator creates a "remote-object" with details about 38 the device and the file descriptor for the device 39 40 - The remaining options are no different from how one launches QEMU with 41 devices. 42 43 - Example command-line for the remote process is as follows: 44 45 /usr/bin/qemu-system-x86_64 \ 46 -machine x-remote \ 47 -device lsi53c895a,id=lsi0 \ 48 -drive id=drive_image2,file=/build/ol7-nvme-test-1.qcow2 \ 49 -device scsi-hd,id=drive2,drive=drive_image2,bus=lsi0.0,scsi-id=0 \ 50 -object x-remote-object,id=robj1,devid=lsi0,fd=4, 51 52* QEMU: 53 54 - Since parts of the RAM are shared between QEMU & remote process, a 55 memory-backend-memfd is required to facilitate this, as follows: 56 57 -object memory-backend-memfd,id=mem,size=2G 58 59 - A "x-pci-proxy-dev" device is created for each of the PCI devices emulated 60 in the remote process. A "socket" sub-option specifies the other end of 61 unix channel created by orchestrator. The "id" sub-option must be specified 62 and should be the same as the "id" specified for the remote PCI device 63 64 - Example commandline for QEMU is as follows: 65 66 -device x-pci-proxy-dev,id=lsi0,socket=3 67