docs/system/multi-process.rst

   1 .. _Multi-process QEMU:
   2
   3 Multi-process QEMU
   4 ==================
   5
   6 This document describes how to configure and use multi-process qemu.
   7 For the design document refer to docs/devel/multi-process.rst.
   8
   9 1) Configuration
  10 ----------------
  11
  12 multi-process is enabled by default for targets that enable KVM
  13
  14
  15 2) Usage
  16 --------
  17
  18 Multi-process QEMU requires an orchestrator to launch.
  19
  20 Following 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