Re: [PATCH v13 00/19] Initial support for multi-process Qemu

[Jag Raman]

Hi,

In this series, we have incorporated the changes Marc-Andre proposed to
improve the code in v12. Following is a changelog that outlines the
differences between v12 and v13.

CHANGELOG:
--------------------

[PATCH v13 02/19] multi-process: add configure and usage information
  - Dropped “tests/multiprocess/multiprocess-lsi53c895a.py” based on
    feedback. We are working on acceptance tests instead.

[PATCH v13 03/19] memory: alloc RAM from file at offset
  - Changed the name of argument “start” to “map_offset”

[PATCH v13 05/19] multi-process: setup PCI host bridge for remote device
  - Renamed MULTIPROCESS_HOST as REMOTE_PCIHOST
  - Also renamed TYPE_REMOTE_HOST_DEVICE and
    REMOTE_HOST_DEVICE as TYPE_REMOTE_PCIHOST and
    REMOTE_PCIHOST respectively

[PATCH v13 06/19] multi-process: setup a machine object for remote device
                  process
  - Renamed “remote-device” as “remote-pcihost”
  - Set a description for the machine class

[PATCH v13 07/19] multi-process: add qio channel function to transmit data
                  and fds
  - Refactored qio_channel_writev_all() and qio_channel_writev_full_all()
    to avoid logic duplication

[PATCH v13 08/19] multi-process: define MPQemuMsg format and transmission
                  functions
  - Introduced qemu_in_iothread() helper function
  - Using ERRP_GUARD to handle input errp parameter
  - Addressed redundant typecasts to “void”
  - mpqemu_msg_send() and mpqemu_msg_send() returns true/false to
    indicate success/failure
  - Added a comment to explain that the messaging protocol used would eventually
    be replaced by vfio-user
  - Prefixed the command enums with “MPQEMU_CMD_”.
  - Skip calling mpqemu_read() if msg->size is zero.

[PATCH v13 09/19] multi-process: Initialize message handler in remote device
  - Check for NULL IOChannel converted to an assert, and moved outside for loop
  - Moved error handling outside for loop
  - Shutdown with SHUTDOWN_CAUSE_HOST_ERROR with error in case of failure
  - Moved exit condition into the for loop statement

[PATCH v13 10/19] multi-process: Associate fd of a PCIDevice with its object
  - Removed a separate header file and merged it into the “.c” file
  - Replaced Object properties with Object Class properties
  - Accept the file descriptor as an integer property, and check if it is a
    valid socket using fd_is_socket()
  - Replaced runtime/dynamic property with a DeviceListener
  - Added a comment to explain the temporary limitation for one device per
    remote process

[PATCH v13 11/19] multi-process: setup memory manager for remote device
  - Dropped the calls to memory_region_transaction_begin() and
    memory_region_transaction_commit()
  - Using ERRP_GUARD to handle input errp parameter
  - Using g_autofree to automatically allocate the “name” variable
  - Moved RET_MSG command definition to the patch that starts to use it

[PATCH v13 12/19] multi-process: introduce proxy object
  - device class property is defined just above the class_init function
  - Using ERRP_GUARD to handle input errp parameter
  - Check if IOChannel is NULL before closing in the exit function, to avoid
    crash
  - Early return if fd is not set
  - dev->migration_blocker is free’d by the exit function alone

[PATCH v13 13/19] multi-process: add proxy communication functions
  - Asset that mpqemu_msg_send_and_await_reply() thread is not in co-routine
    context
  - Using ERRP_GUARD to handle input errp parameter

[PATCH v13 14/19] multi-process: Forward PCI config space acceses to the
                  remote process
  - process_config_write() & process_config_read() take an Error** argument to
    return error
  - Use FMT_pid to format messages with PID
  - Use error_prepend to avoid leak of Error*
  - Check if return value from remote indicates failure in config_op_send()
  - Dropped typecasting return values of config_op_send to void as it’s not
    necessary

[PATCH v13 16/19] multi-process: Synchronize remote memory
  - Renamed RemoteMemSync as ProxyMemoryListener
  - Prefixed all related functions with “proxy_memory_listener_” for consistency
  - Simplify logic in proxy_mrs_can_merge() to return efficiently and avoid
    unnecessary definition of local variable.

[PATCH v13 17/19] multi-process: create IOHUB object to handle irq
  - Replace calls to qemu_mutex_lock() and qemu_mutex_unlock() with
    QEMU_LOCK_GUARD

Thank you very much!

> On Dec 14, 2020, at 12:14 AM, Jagannathan Raman <jag.raman@oracle.com> wrote:
> 
> Hello,
> 
> This is the v13 of the patchset. Thank you very much for reviewing v12 and
> sharing your feedback.
> 
> We have addressed all the comments from the v12 review except for the
> following two items, which we will be addressing in subsequent patches:
> - Prefix log messages with PID in the logging subsystem.
> - Refactor vfio-user and multi-process code to avoid logic duplication.
> 
> To touch upon the history of this project, we posted the Proof Of Concept
> patches before the BoF session in 2018. Subsequently, we have posted 12
> versions on the qemu-devel mailing list. You can find them by following the
> links below ([1] - [12]). Following people contributed to the design and
> implementation of this project:
> Jagannathan Raman <jag.raman@oracle.com>
> Elena Ufimtseva <elena.ufimtseva@oracle.com>
> John G Johnson <john.g.johnson@oracle.com>
> Stefan Hajnoczi <stefanha@redhat.com>
> Konrad Wilk <konrad.wilk@oracle.com>
> Kanth Ghatraju <kanth.ghatraju@oracle.com>
> 
> We would like to thank the QEMU community for your feedback in the
> design and implementation of this project. Qemu wiki page:
> https://wiki.qemu.org/Features/MultiProcessQEMU
> 
> For the full concept writeup about QEMU multi-process, please
> refer to docs/devel/qemu-multiprocess.rst. Also, see
> docs/qemu-multiprocess.txt for usage information.
> 
> We have retained Stefan's "Reviewed-by" in the commit messages. Thank you
> very much for your time in reviewing these patches!
> 
> [POC]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg566538.html
> [1]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg602285.html
> [2]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg624877.html
> [3]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg642000.html
> [4]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg655118.html
> [5]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg682429.html
> [6]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg697484.html
> [7]: https://patchew.org/QEMU/cover.1593273671.git.elena.ufimtseva@oracle.com/
> [8]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg727007.html
> [9]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg734275.html
> [10]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg747638.html
> [11]: https://www.mail-archive.com/qemu-devel@nongnu.org/msg750972.html
> [12]: cover.1606853298.git.jag.raman@oracle.com/">https://patchew.org/QEMU/cover.1606853298.git.jag.raman@oracle.com/
> 
> Elena Ufimtseva (7):
>  multi-process: add configure and usage information
>  multi-process: add qio channel function to transmit data and fds
>  multi-process: define MPQemuMsg format and transmission functions
>  multi-process: introduce proxy object
>  multi-process: add proxy communication functions
>  multi-process: Forward PCI config space acceses to the remote process
>  multi-process: perform device reset in the remote process
> 
> Jagannathan Raman (11):
>  memory: alloc RAM from file at offset
>  multi-process: Add config option for multi-process QEMU
>  multi-process: setup PCI host bridge for remote device
>  multi-process: setup a machine object for remote device process
>  multi-process: Initialize message handler in remote device
>  multi-process: Associate fd of a PCIDevice with its object
>  multi-process: setup memory manager for remote device
>  multi-process: PCI BAR read/write handling for proxy & remote
>    endpoints
>  multi-process: Synchronize remote memory
>  multi-process: create IOHUB object to handle irq
>  multi-process: Retrieve PCI info from remote process
> 
> John G Johnson (1):
>  multi-process: add the concept description to
>    docs/devel/qemu-multiprocess
> 
> docs/devel/index.rst                      |   1 +
> docs/devel/multi-process.rst              | 966 ++++++++++++++++++++++++++++++
> docs/multi-process.rst                    |  64 ++
> meson.build                               |   1 +
> hw/remote/trace.h                         |   1 +
> include/exec/memory.h                     |   2 +
> include/exec/ram_addr.h                   |   2 +-
> include/hw/pci-host/remote.h              |  31 +
> include/hw/pci/pci_ids.h                  |   3 +
> include/hw/remote/iohub.h                 |  42 ++
> include/hw/remote/machine.h               |  40 ++
> include/hw/remote/memory.h                |  19 +
> include/hw/remote/mpqemu-link.h           |  99 +++
> include/hw/remote/proxy-memory-listener.h |  28 +
> include/hw/remote/proxy.h                 |  52 ++
> include/io/channel.h                      |  50 ++
> include/qemu/mmap-alloc.h                 |   4 +-
> include/sysemu/iothread.h                 |   6 +
> backends/hostmem-memfd.c                  |   2 +-
> hw/misc/ivshmem.c                         |   3 +-
> hw/pci-host/remote.c                      |  75 +++
> hw/remote/iohub.c                         | 119 ++++
> hw/remote/machine.c                       |  80 +++
> hw/remote/memory.c                        |  65 ++
> hw/remote/message.c                       | 230 +++++++
> hw/remote/mpqemu-link.c                   | 267 +++++++++
> hw/remote/proxy-memory-listener.c         | 227 +++++++
> hw/remote/proxy.c                         | 371 ++++++++++++
> hw/remote/remote-obj.c                    | 206 +++++++
> io/channel.c                              |  63 +-
> iothread.c                                |   6 +
> softmmu/memory.c                          |   3 +-
> softmmu/physmem.c                         |  11 +-
> util/mmap-alloc.c                         |   7 +-
> util/oslib-posix.c                        |   2 +-
> MAINTAINERS                               |  24 +
> accel/Kconfig                             |   1 +
> hw/Kconfig                                |   1 +
> hw/meson.build                            |   1 +
> hw/pci-host/Kconfig                       |   3 +
> hw/pci-host/meson.build                   |   1 +
> hw/remote/Kconfig                         |   4 +
> hw/remote/meson.build                     |  13 +
> hw/remote/trace-events                    |   4 +
> 44 files changed, 3186 insertions(+), 14 deletions(-)
> create mode 100644 docs/devel/multi-process.rst
> create mode 100644 docs/multi-process.rst
> create mode 100644 hw/remote/trace.h
> create mode 100644 include/hw/pci-host/remote.h
> create mode 100644 include/hw/remote/iohub.h
> create mode 100644 include/hw/remote/machine.h
> create mode 100644 include/hw/remote/memory.h
> create mode 100644 include/hw/remote/mpqemu-link.h
> create mode 100644 include/hw/remote/proxy-memory-listener.h
> create mode 100644 include/hw/remote/proxy.h
> create mode 100644 hw/pci-host/remote.c
> create mode 100644 hw/remote/iohub.c
> create mode 100644 hw/remote/machine.c
> create mode 100644 hw/remote/memory.c
> create mode 100644 hw/remote/message.c
> create mode 100644 hw/remote/mpqemu-link.c
> create mode 100644 hw/remote/proxy-memory-listener.c
> create mode 100644 hw/remote/proxy.c
> create mode 100644 hw/remote/remote-obj.c
> create mode 100644 hw/remote/Kconfig
> create mode 100644 hw/remote/meson.build
> create mode 100644 hw/remote/trace-events
> 
> -- 
> 1.8.3.1
>