On Wed, 3 Aug 2016 17:22:36 +0100 "Daniel P. Berrange" <berra...@redhat.com> wrote:
> The virtio-console.c file handles both serial consoles > and interactive consoles, since they're backed by the > same device model. > > Since serial devices are expected to be reliable and > need to notify the guest when the backend is opened > or closed, the virtio-console.c file wires up support > for chardev events. This affects both serial consoles > and interactive consoles, using a network connection > based chardev backend such as 'socket', but not when > using a PTY based backend or plain 'file' backends. > > When the host side is not connected the handle_output() > method in virtio-serial-bus.c will drop any data sent > by the guest, before it even reaches the virtio-console.c > code. This means that if the chardev has a logfile > configured, the data will never get logged. > > Consider for example, configuring a x86_64 guest with a > plain UART serial port > > -chardev > socket,id=charserial1,host=127.0.0.1,port=9001,server,nowait,logfile=console1.log,logappend=on > -device isa-serial,chardev=charserial1,id=serial1 > > vs a s390 guest which has to use the virtio-console port > > -chardev > socket,id=charconsole1,host=127.0.0.1,port=9000,server,nowait,logfile=console2.log,logappend=on > -device virtconsole,chardev=charconsole1,id=console1 > > The isa-serial one gets data written to the log regardless > of whether a client is connected, while the virtioconsole > one only gets data written to the log when a client is > connected. > > There is no need for virtio-serial-bus.c to aggressively > drop the data for console devices, as the chardev code is > prefectly capable of discarding the data itself. > > So this patch changes virtconsole devices so that they > are always marked as having the host side open. This > ensures that the guest OS will always send any data it > has (Linux virtio-console hvc driver actually ignores > the host open state and sends data regardless, but we > should not rely on that), and also prevents the > virtio-serial-bus code prematurely discarding data. > > The behaviour of virtserialport devices is *not* changed, > only virtconsole, because for the former, it is important > that the guest OSknow exactly when the host side is opened > / closed so it can do any protocol re-negotiation that may > be required. > > Fixes bug: https://bugs.launchpad.net/qemu/+bug/1599214 > > Signed-off-by: Daniel P. Berrange <berra...@redhat.com> > --- > hw/char/virtio-console.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) From my limited understanding of the character layer this sounds reasonable, and I agree that this is 2.7 material. Acked-by: Cornelia Huck <cornelia.h...@de.ibm.com>
