| Message ID | 1470241360-3574-2-git-send-email-berrange@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 03/08/2016 18:22, Daniel P. Berrange 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 <berrange@redhat.com> > --- > hw/char/virtio-console.c | 25 +++++++++++++++++++++---- > 1 file changed, 21 insertions(+), 4 deletions(-) > > diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c > index 2e36481..4f0e03d 100644 > --- a/hw/char/virtio-console.c > +++ b/hw/char/virtio-console.c > @@ -85,8 +85,9 @@ static void set_guest_connected(VirtIOSerialPort *port, int guest_connected) > { > VirtConsole *vcon = VIRTIO_CONSOLE(port); > DeviceState *dev = DEVICE(port); > + VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port); > > - if (vcon->chr) { > + if (vcon->chr && !k->is_console) { > qemu_chr_fe_set_open(vcon->chr, guest_connected); > } > > @@ -156,9 +157,25 @@ static void virtconsole_realize(DeviceState *dev, Error **errp) > } > > if (vcon->chr) { > - vcon->chr->explicit_fe_open = 1; > - qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, chr_event, > - vcon); > + /* > + * For consoles we don't block guest data transfer just > + * because nothing is connected - we'll just let it go > + * whetherever the chardev wants - /dev/null probably. > + * > + * For serial ports we need 100% reliable data transfer > + * so we use the opened/closed signals from chardev to > + * trigger open/close of the device > + */ > + if (k->is_console) { > + vcon->chr->explicit_fe_open = 0; > + qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, > + NULL, vcon); > + virtio_serial_open(port); > + } else { > + vcon->chr->explicit_fe_open = 1; > + qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, > + chr_event, vcon); > + } > } > } > > I think this patch should go in 2.7, perhaps patch 2 too. Everything else can wait for 2.8. Paolo
On Wed, 3 Aug 2016 17:22:36 +0100 "Daniel P. Berrange" <berrange@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 <berrange@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.huck@de.ibm.com>
diff --git a/hw/char/virtio-console.c b/hw/char/virtio-console.c index 2e36481..4f0e03d 100644 --- a/hw/char/virtio-console.c +++ b/hw/char/virtio-console.c @@ -85,8 +85,9 @@ static void set_guest_connected(VirtIOSerialPort *port, int guest_connected) { VirtConsole *vcon = VIRTIO_CONSOLE(port); DeviceState *dev = DEVICE(port); + VirtIOSerialPortClass *k = VIRTIO_SERIAL_PORT_GET_CLASS(port); - if (vcon->chr) { + if (vcon->chr && !k->is_console) { qemu_chr_fe_set_open(vcon->chr, guest_connected); } @@ -156,9 +157,25 @@ static void virtconsole_realize(DeviceState *dev, Error **errp) } if (vcon->chr) { - vcon->chr->explicit_fe_open = 1; - qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, chr_event, - vcon); + /* + * For consoles we don't block guest data transfer just + * because nothing is connected - we'll just let it go + * whetherever the chardev wants - /dev/null probably. + * + * For serial ports we need 100% reliable data transfer + * so we use the opened/closed signals from chardev to + * trigger open/close of the device + */ + if (k->is_console) { + vcon->chr->explicit_fe_open = 0; + qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, + NULL, vcon); + virtio_serial_open(port); + } else { + vcon->chr->explicit_fe_open = 1; + qemu_chr_add_handlers(vcon->chr, chr_can_read, chr_read, + chr_event, vcon); + } } }
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 <berrange@redhat.com> --- hw/char/virtio-console.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-)