[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 2/3] hvc_init(): Enforce one-time initialization.
Good grief! Sorry for the spacing mess-up! Here's a resend with reformatting. Amit, We aren't using either QEMU or kvmtool, but we are using KVM. All the issues we are seeing happen when we try to establish multiple virtioconsoles at boot time. The command line isn't relevant, but I can tell you the protocol that's passing between the host (kvm) and the guest (see the end of this message). We do go through the control_work_handler(), but it's not providing synchronization. Here's a trace of the control_work_handler() and handle_control_message() calls; note that there are two concurrent calls to control_work_handler(). I decorated control_work_handler() with a "lifetime" marker, and passed this value to handle_control_message(), so we can see which control messages are being handled from which instance of the control_work_handler() thread. Notice that we enter control_work_handler() a second time before the handling of the second PORT_ADD message is complete. The first CONSOLE_PORT message is handled by the second control_work_handler() call, but the second is handled by the first control_work_handler() call. root@myubuntu:~# dmesg | grep MBH [3371055.808738] control_work_handler #1 [3371055.809372] + #1 handle_control_message PORT_ADD [3371055.810169] - handle_control_message PORT_ADD [3371055.810170] + #1 handle_control_message PORT_ADD [3371055.810244] control_work_handler #2 [3371055.810245] + #2 handle_control_message CONSOLE_PORT [3371055.810246] got hvc_ports_mutex [3371055.810578] - handle_control_message PORT_ADD [3371055.810579] + #1 handle_control_message CONSOLE_PORT [3371055.810580] trylock of hvc_ports_mutex failed [3371055.811352] got hvc_ports_mutex [3371055.811370] - handle_control_message CONSOLE_PORT [3371055.816609] - handle_control_message CONSOLE_PORT So, I'm guessing the bug is that there shouldn't be two instances of control_work_handler() running simultaneously? Thanks, Miche Protocol: We set up the virtio console device registers during initialization, specifying the multiport feature, and some number of ports, n, where nis greater than 1. In the guest, virtcons_probe() finds our device, and successfully sends the VIRTIO_CONSOLE_DEVICE_READY=1 control message. On the host, we receive the VIRTIO_CONSOLE_DEVICE_READY message, and send one VIRTIO_CONSOLE_PORT_ADD message via the Receive Control queuefor each port in the number of ports. These messages are not serialized: they are all sent at once. The VIRTIO_CONSOLE_PORT_ADD messages are received in handle_control_message() in virtio_console.c, and add_port() is called for each. After each port is added, the guest sendsVIRTIO_CONSOLE_PORT_READY to the host, and in these messages, the id of the port is included in the message. On the host, in response to each VIRTIO_CONSOLE_PORT_READY=1 message, we may send a VIRTIO_CONSOLE_CONSOLE_PORT message. On the guest, in response to each VIRTIO_CONSOLE_CONSOLE_PORT message, init_port_console() is called on the individual port. The same id is used for these messages as was used for the PORT_READY messages. After each successful init_port_console(), the guest sends VIRTIO_CONSOLE_PORT_OPEN back to the host. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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