[v15,02/20] multi-process: add configure and usage information

Commit Message

Elena Ufimtseva Dec. 23, 2020, 6:14 a.m. UTC

From: Elena Ufimtseva <[e-mail]>

Adds documentation explaining the command-line arguments needed
to use multi-process.

Signed-off-by: Elena Ufimtseva <[e-mail]>
Signed-off-by: Jagannathan Raman <[e-mail]>
Signed-off-by: John G Johnson <[e-mail]>
Reviewed-by: Stefan Hajnoczi <[e-mail]>
---
 docs/multi-process.rst | 64 ++++++++++++++++++++++++++++++++++++++++++
 MAINTAINERS            |  1 +
 2 files changed, 65 insertions(+)
 create mode 100644 docs/multi-process.rst

Patch

diff --git a/docs/multi-process.rst b/docs/multi-process.rst
new file mode 100644
index 0000000000..46bb0cafc2
--- /dev/null
+++ b/docs/multi-process.rst
@@ -0,0 +1,64 @@ 
+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
+----------------
+
+multi-process is enabled by default for targets that enable KVM
+
+
+2) Usage
+--------
+
+Multi-process QEMU requires an orchestrator to launch.
+
+Following is a description of command-line used to launch mpqemu.
+
+* Orchestrator:
+
+  - The Orchestrator creates a unix socketpair
+
+  - It launches the remote process and passes one of the
+    sockets to it via command-line.
+
+  - It then launches QEMU and specifies the other socket as an option
+    to the Proxy device object
+
+* Remote Process:
+
+  - QEMU can enter remote process mode by using the "remote" machine
+    option.
+
+  - The orchestrator creates a "remote-object" with details about
+    the device and the file descriptor for the device
+
+  - The remaining options are no different from how one launches QEMU with
+    devices.
+
+  - Example command-line for the remote process is as follows:
+
+      /usr/bin/qemu-system-x86_64                                        \
+      -machine x-remote                                                  \
+      -device lsi53c895a,id=lsi0                                         \
+      -drive id=drive_image2,file=/build/ol7-nvme-test-1.qcow2           \
+      -device scsi-hd,id=drive2,drive=drive_image2,bus=lsi0.0,scsi-id=0  \
+      -object x-remote-object,id=robj1,devid=lsi1,fd=4,
+
+* QEMU:
+
+  - Since parts of the RAM are shared between QEMU & remote process, a
+    memory-backend-memfd is required to facilitate this, as follows:
+
+    -object memory-backend-memfd,id=mem,size=2G
+
+  - A "x-pci-proxy-dev" device is created for each of the PCI devices emulated
+    in the remote process. A "socket" sub-option specifies the other end of
+    unix channel created by orchestrator. The "id" sub-option must be specified
+    and should be the same as the "id" specified for the remote PCI device
+
+  - Example commandline for QEMU is as follows:
+
+      -device x-pci-proxy-dev,id=lsi0,socket=3
diff --git a/MAINTAINERS b/MAINTAINERS
index 395e215236..c9f7024943 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3163,6 +3163,7 @@  M: Jagannathan Raman <[e-mail]>
 M: John G Johnson <[e-mail]>
 S: Maintained
 F: docs/devel/multi-process.rst
+F: docs/multi-process.rst
 
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