docs/system/multi-process.rst

   1 Multi-process QEMU
   2 ==================
   3
   4 This document describes how to configure and use multi-process qemu.
   5 For the design document refer to docs/devel/qemu-multiprocess.
   6
   7 1) Configuration
   8 ----------------
   9
  10 multi-process is enabled by default for targets that enable KVM
  11
  12
  13 2) Usage
  14 --------
  15
  16 Multi-process QEMU requires an orchestrator to launch.
  17
  18 Following 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=lsi0,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