Virtio Serial fails to connect to name pipe on Windows

Running openvmm.exe with the options --virtio-serial=term --virtio-console opens a new terminal window, but it does not appear to be connected to anything. These options launch a child process to copy data back and forth from a named pipe (openvmm.exe --relay-console-path \\.\pipe\219476404589302878345095266126242352181 --relay-console-title "VIRTIO_SERIAL [OpenVMM]"), but this process silently exits immediately with the error code

0:000> !gle
LastErrorValue: (Win32) 0x6d (109) - The pipe has been ended.
LastStatusValue: (NTSTATUS) 0xc000014b - The pipe operation has failed because the other end of the pipe has been closed.

This leaves an orphaned terminal window behind with the title "VIRTIO_SERIAL [OpenVMM]", but there is nothing reading or writing to/from its stdin/stdio.

I'm not entirely sure where the failure is occurring in the code, I captured a ttd trace of the process, but windbg is having a hard time with the async closure in openvmm!console_relay::relay_console. I also don't see any logging coming from this process; I collected ETW events from the Microsoft.HvLite provider, but I don't see any events from this child process.

Start with the console_relay::relay_console path and reproduce the issue using openvmm.exe --virtio-serial=term --virtio-console. Trace the child process and named-pipe connection around the reported ERROR_BROKEN_PIPE failure. Done means the virtio serial terminal connects successfully and does not leave an orphaned window.