On 2/22/23 01:35, Laine Stump wrote: > If the passt process that implements the backend of a QEMU emulated > network device terminates, QEMU itself is incapable of restarting a > new process so that the networking can begin... working again. > > However, what QEMU can and does do is: > > 1) send the NETDEV_STREAM_DISCONNECTED event to libvirt when it sees > that the socket has been closed (this event has been in QEMU for as > long as support for "-netdev stream", which is used for connecting > to passt) > > 2) as of QEMU 8.0.0, the qemu commandline for -netdev stream accepts > the "reconnect" option, which tells QEMU to attempt reconnecting to > the same socket it previously used, repeating the attempt every "n" > seconds (the only argument to reconnect) until it is successful. > > If libvirt adds the reconnect option to the qemu commandline, and then > responds to a NETDEV_STREAM_DISCONNECTED event by re-running the same > passt command that it ran when the device was originally connected, > then a guest will be able to recover in the (very unlikely, according > to Stefano!) event that the original passt process unexpectedly exits, > or is killed by some external entity. > > Patch 2/3 handles (2) above, while patch 3/3 handles (1). (patch 1/3 > is a short guest appearance by pkrempa. Thanks pkrempa!). > > This resolves https://bugzilla.redhat.com/2172098 > > Along with Stefano's series fixing up selinux issues related to > running the passt process, they make the passt backend very usable. > > Laine Stump (2): > qemu: add reconnect=5 to passt qemu commandline options when available > qemu: respond to NETDEV_STREAM_DISCONNECTED event > > Peter Krempa (1): > qemu: capabilities: Introduce QEMU_CAPS_NETDEV_STREAM_RECONNECT > > src/qemu/qemu_capabilities.c | 4 + > src/qemu/qemu_capabilities.h | 3 + > src/qemu/qemu_domain.c | 1 + > src/qemu/qemu_domain.h | 1 + > src/qemu/qemu_driver.c | 82 +++++++++++++++++++ > src/qemu/qemu_monitor.c | 11 +++ > src/qemu/qemu_monitor.h | 6 ++ > src/qemu/qemu_monitor_json.c | 16 ++++ > src/qemu/qemu_passt.c | 11 +++ > src/qemu/qemu_process.c | 18 ++++ > .../caps_8.0.0.x86_64.xml | 1 + > .../net-user-passt.x86_64-7.2.0.args | 37 +++++++++ > .../net-user-passt.x86_64-latest.args | 2 +- > tests/qemuxml2argvtest.c | 1 + > 14 files changed, 193 insertions(+), 1 deletion(-) > create mode 100644 tests/qemuxml2argvdata/net-user-passt.x86_64-7.2.0.args > Reviewed-by: Michal Privoznik <mprivozn@xxxxxxxxxx> Michal
