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a8aa6197a2
The following behavior was observed for QEMU configured by libvirt to use guest agent as usual for the guests without virtio-serial driver (Windows or the guest remaining in BIOS stage). In QEMU on first connect to listen character device socket the listen socket is removed from poll just after the accept(). virtio_serial_guest_ready() returns 0 and the descriptor of the connected Unix socket is removed from poll and it will not be present in poll() until the guest will initialize the driver and change the state of the serial to "guest connected". In libvirt connect() to guest agent is performed on restart and is run under VM state lock. Connect() is blocking and can wait forever. In this case libvirt can not perform ANY operation on that VM. The bug can be easily reproduced this way: Terminal 1: qemu-system-x86_64 -m 512 -device pci-serial,chardev=serial1 -chardev socket,id=serial1,path=/tmp/console.sock,server,nowait (virtio-serial and isa-serial also fit) Terminal 2: minicom -D unix\#/tmp/console.sock (type something and press enter) C-a x (to exit) Do 3 times: minicom -D unix\#/tmp/console.sock C-a x It needs 4 connections, because the first one is accepted by QEMU, then two are queued by the kernel, and the 4th blocks. The problem is that QEMU doesn't add a read watcher after succesful read until the guest device wants to acquire recieved data, so I propose to install a separate pullhup watcher regardless of whether the device waits for data or not. Signed-off-by: Klim Kireev <klim.kireev@virtuozzo.com> Message-Id: <20180125135129.9305-1-klim.kireev@virtuozzo.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
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| .. | ||
| baum.c | ||
| char-console.c | ||
| char-fd.c | ||
| char-fe.c | ||
| char-file.c | ||
| char-io.c | ||
| char-mux.c | ||
| char-null.c | ||
| char-parallel.c | ||
| char-pipe.c | ||
| char-pty.c | ||
| char-ringbuf.c | ||
| char-serial.c | ||
| char-socket.c | ||
| char-stdio.c | ||
| char-udp.c | ||
| char-win-stdio.c | ||
| char-win.c | ||
| char.c | ||
| Makefile.objs | ||
| msmouse.c | ||
| spice.c | ||
| testdev.c | ||
| trace-events | ||
| wctablet.c | ||