LXR qemu/docs/system/multi-process.rst

   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