Re: [PATCH v12 02/19] multi-process: add configure and usage information

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Dec 01, 2020 at 03:22:37PM -0500, Jagannathan Raman wrote:
> From: Elena Ufimtseva <elena.ufimtseva@oracle.com>
> 
> Adds documentation explaining the command-line arguments needed
> to use multi-process. Also adds a python script that illustrates the
> usage.
> 
> Signed-off-by: Elena Ufimtseva <elena.ufimtseva@oracle.com>
> Signed-off-by: Jagannathan Raman <jag.raman@oracle.com>
> Signed-off-by: John G Johnson <john.g.johnson@oracle.com>
> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  docs/multi-process.rst                        | 66 +++++++++++++++++++
>  MAINTAINERS                                   |  1 +
>  tests/multiprocess/multiprocess-lsi53c895a.py | 92 +++++++++++++++++++++++++++
>  3 files changed, 159 insertions(+)
>  create mode 100644 docs/multi-process.rst
>  create mode 100755 tests/multiprocess/multiprocess-lsi53c895a.py


> diff --git a/tests/multiprocess/multiprocess-lsi53c895a.py b/tests/multiprocess/multiprocess-lsi53c895a.py
> new file mode 100755
> index 0000000..bfe4f66
> --- /dev/null
> +++ b/tests/multiprocess/multiprocess-lsi53c895a.py
> @@ -0,0 +1,92 @@
> +#!/usr/bin/env python3
> +
> +import urllib.request
> +import subprocess
> +import argparse
> +import socket
> +import sys
> +import os
> +
> +arch = os.uname()[4]
> +proc_path = os.path.join(os.getcwd(), '..', '..', 'build', arch+'-softmmu',
> +                         'qemu-system-'+arch)
> +
> +parser = argparse.ArgumentParser(description='Launcher for multi-process QEMU')
> +parser.add_argument('--bin', required=False, help='location of QEMU binary',
> +                    metavar='bin');
> +args = parser.parse_args()
> +
> +if args.bin is not None:
> +    proc_path = args.bin
> +
> +if not os.path.isfile(proc_path):
> +    sys.exit('QEMU binary not found')
> +
> +kernel_path = os.path.join(os.getcwd(), 'vmlinuz')
> +initrd_path = os.path.join(os.getcwd(), 'initrd')
> +
> +proxy_cmd = [ proc_path,                                                    \
> +              '-name', 'Fedora', '-smp', '4', '-m', '2048', '-cpu', 'host', \

I wonder if setting 2 GB of RAM is too large for something that runs by
default as a test.

> +              '-object', 'memory-backend-memfd,id=sysmem-file,size=2G',     \
> +              '-numa', 'node,memdev=sysmem-file',                           \
> +              '-kernel', kernel_path, '-initrd', initrd_path,               \
> +              '-vnc', ':0',                                                 \
> +              '-monitor', 'unix:/home/qemu-sock,server,nowait',             \
> +            ]
> +
> +if arch == 'x86_64':
> +    print('Downloading images for arch x86_64')
> +    kernel_url = 'https://dl.fedoraproject.org/pub/fedora/linux/'    \
> +                 'releases/33/Everything/x86_64/os/images/'          \
> +                 'pxeboot/vmlinuz'
> +    initrd_url = 'https://dl.fedoraproject.org/pub/fedora/linux/'    \
> +                 'releases/33/Everything/x86_64/os/images/'          \
> +                 'pxeboot/initrd.img'
> +    proxy_cmd.append('-machine')
> +    proxy_cmd.append('pc,accel=kvm')
> +    proxy_cmd.append('-append')
> +    proxy_cmd.append('rdinit=/bin/bash console=ttyS0 console=tty0')
> +elif arch == 'aarch64':
> +    print('Downloading images for arch aarch64')
> +    kernel_url = 'https://dl.fedoraproject.org/pub/fedora/linux/'    \
> +                 'releases/33/Everything/aarch64/os/images/'         \
> +                 'pxeboot/vmlinuz'
> +    initrd_url = 'https://dl.fedoraproject.org/pub/fedora/linux/'    \
> +                 'releases/33/Everything/aarch64/os/images/'         \
> +                 'pxeboot/initrd.img'
> +    proxy_cmd.append('-machine')
> +    proxy_cmd.append('virt,gic-version=3')
> +    proxy_cmd.append('-accel')
> +    proxy_cmd.append('kvm')
> +    proxy_cmd.append('-append')
> +    proxy_cmd.append('rdinit=/bin/bash')
> +else:
> +    sys.exit('Arch %s not tested' % arch)

It doens't look like you really need a full OS here. Rather than
downloading the fairly large Fedora images, I'd suggest just using
the kernel that exists on the host OS already in /boot, and then
building a tiny initrd that contains just a static linked busybox.

I have this helper script that could be imported into QEMU for
this purpose:

  https://gitlab.com/berrange/tiny-vm-tools/-/blob/master/make-tiny-image.py

And just skip the test if busybox doesn't exist, or if the vmlinux
in /boot isn't accessible (Debian restricts it to root only IIRC)

> +
> +urllib.request.urlretrieve(kernel_url, kernel_path)
> +urllib.request.urlretrieve(initrd_url, initrd_path)
> +
> +proxy, remote = socket.socketpair(socket.AF_UNIX, socket.SOCK_STREAM)
> +
> +proxy_cmd.append('-device')
> +proxy_cmd.append('x-pci-proxy-dev,id=lsi1,fd='+str(proxy.fileno()))
> +
> +remote_cmd = [ proc_path,                                                      \
> +               '-machine', 'x-remote',                                         \
> +               '-device', 'lsi53c895a,id=lsi1',                                \
> +               '-object',                                                      \
> +               'x-remote-object,id=robj1,devid=lsi1,fd='+str(remote.fileno()), \
> +               '-display', 'none',                                             \
> +               '-monitor', 'unix:/home/rem-sock,server,nowait',                \
> +             ]
> +
> +pid = os.fork();
> +
> +if pid:
> +    # In Proxy
> +    print('Launching QEMU with Proxy object');
> +    process = subprocess.Popen(proxy_cmd, pass_fds=[proxy.fileno()])
> +else:
> +    # In remote
> +    print('Launching Remote process');
> +    process = subprocess.Popen(remote_cmd, pass_fds=[remote.fileno(), 0, 1, 2])

Regards,
Daniel
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