Merge remote-tracking branch 'remotes/stefanha-gitlab/tags/block-pull-request' into staging

Pull request

v4:
 * Add PCI_EXPRESS Kconfig dependency to fix s390x in "multi-process: setup PCI
   host bridge for remote device" [Philippe and Thomas]

# gpg: Signature made Wed 10 Feb 2021 09:26:14 GMT
# gpg:                using RSA key 8695A8BFD3F97CDAAC35775A9CA4ABB381AB73C8
# gpg: Good signature from "Stefan Hajnoczi <stefanha@redhat.com>" [full]
# gpg:                 aka "Stefan Hajnoczi <stefanha@gmail.com>" [full]
# Primary key fingerprint: 8695 A8BF D3F9 7CDA AC35  775A 9CA4 ABB3 81AB 73C8

* remotes/stefanha-gitlab/tags/block-pull-request: (27 commits)
  docs: fix Parallels Image "dirty bitmap" section
  multi-process: perform device reset in the remote process
  multi-process: Retrieve PCI info from remote process
  multi-process: create IOHUB object to handle irq
  multi-process: Synchronize remote memory
  multi-process: PCI BAR read/write handling for proxy & remote endpoints
  multi-process: Forward PCI config space acceses to the remote process
  multi-process: add proxy communication functions
  multi-process: introduce proxy object
  multi-process: setup memory manager for remote device
  multi-process: Associate fd of a PCIDevice with its object
  multi-process: Initialize message handler in remote device
  multi-process: define MPQemuMsg format and transmission functions
  io: add qio_channel_readv_full_all_eof & qio_channel_readv_full_all helpers
  io: add qio_channel_writev_full_all helper
  multi-process: setup a machine object for remote device process
  multi-process: setup PCI host bridge for remote device
  multi-process: Add config option for multi-process QEMU
  memory: alloc RAM from file at offset
  multi-process: add configure and usage information
  ...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 64 insertions, 0 deletions

diff --git a/docs/system/multi-process.rst b/docs/system/multi-process.rst
new file mode 100644
index 0000000000..46bb0cafc2
--- /dev/null
+++ b/docs/system/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