[RFC,v3,45/45] multi-process: add configure and usage information

Commit Message

Jag Raman Sept. 3, 2019, 8:38 p.m. UTC

From: Elena Ufimtseva <[e-mail]>

Signed-off-by: Elena Ufimtseva <[e-mail]>
Signed-off-by: Jagannathan Raman <[e-mail]>
Signed-off-by: John G Johnson <[e-mail]>
---
Changes in v3:
 - since the changes were made to use existing device/drive options,
the document was modified to reflect this.
---
 docs/qemu-multiprocess.txt | 86 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 docs/qemu-multiprocess.txt

Patch

diff --git a/docs/qemu-multiprocess.txt b/docs/qemu-multiprocess.txt
new file mode 100644
index 0000000..c29f4df
--- /dev/null
+++ b/docs/qemu-multiprocess.txt
@@ -0,0 +1,86 @@ 
+Multi-process QEMU
+==================
+
+This document describes how to configure and use multi-process qemu.
+For the design document refer to docs/devel/qemu-multiprocess.
+
+1) Configuration
+----------------
+
+To enable support for multi-process add --enable-mpqemu
+to the list of options for the "configure" script.
+
+
+2) Usage
+--------
+
+To start qemu with devices intended to run in a separate emulation
+process without libvirtd support, the following should be used on QEMU
+command line. As of now, we only support the emulation of lsi53c895a
+in a separate process
+
+* Since parts of the RAM are shared between QEMU & remote process, a
+  memory-backend-file is required to facilitate this, as follows:
+
+  -object memory-backend-file,id=mem,mem-path=/dev/shm/,size=4096M,share=on
+
+* The devices to be emulated in the separate process are defined as
+  before with addition of "rid" suboption that serves as a remote group
+  identificator.
+
+  -device <device options>,rid="remote process id"
+
+  For exmaple, for non multi-process qemu:
+    -device lsi53c895a,id=scsi0 device
+    -device scsi-hd,drive=drive0,bus=scsi0.0,scsi-id=0
+    -drive id=drive0,file=data-disk.img
+
+  and for multi-process qemu and no libvirt
+  support (i.e. QEMU forks child processes):
+    -device lsi53c895a,id=scsi0,rid=0
+    -device scsi-hd,drive=drive0,bus=scsi0.0,scsi-id=0,rid="0"
+
+* The command-line options for the remote process is added to the "command"
+  suboption of the newly added "-remote" option. 
+
+   -remote [socket],rid=,command="..."
+
+  The drives to be emulated by the remote process are specified as part of
+  this command sub-option. The device to be used to connect to the monitor
+  is also specified as part of this suboption.
+
+  For example, the following option adds a drive and monitor to the remote
+  process:
+  -remote rid=0,command="-drive id=drive0,,file=data-disk.img -monitor unix:/home/qmp-sock,,server,,nowait"
+
+  Note: There's an issue with this "command" subtion which we are in the
+  process of fixing. To work around this issue, it requires additional
+  "comma" characters as illustrated above, and in the example below.
+
+* Example QEMU command-line to launch lsi53c895a in a remote process
+
+  #/bin/sh
+  qemu-system-x86_64 \
+  -name "OL7.4" \
+  -machine q35,accel=kvm \
+  -smp sockets=1,cores=1,threads=1 \
+  -cpu host \
+  -m 2048 \
+  -object memory-backend-file,id=mem,mem-path=/dev/shm/,size=2G,share=on \
+  -numa node,memdev=mem \
+  -device virtio-scsi-pci,id=virtio_scsi_pci0 \
+  -drive id=drive_image1,if=none,format=raw,file=/root/ol7.qcow2 \
+  -device scsi-hd,id=image1,drive=drive_image1,bus=virtio_scsi_pci0.0 \
+  -boot d \
+  -monitor stdio \
+  -vnc :0 \
+  -device lsi53c895a,id=lsi0,remote,rid=8,command="qemu-scsi-dev" \
+  -device scsi-hd,id=drive2,drive=drive_image2,bus=lsi0.0,scsi-id=0,remote,rid=8,command="qemu-scsi-dev"\
+  -remote rid=8,command="-drive id=drive_image2,,file=/root/remote-process-disk.img -monitor unix:/home/qmp-sock,,server,,nowait"
+
+  We could connect to the monitor using the following command:
+  socat /home/qmp-sock stdio
+
+  After hotplugging disks to the remote process, please execute the
+  following command in the guest to refresh the list of storage devices:
+  rescan_scsi_bus.sh -a