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[Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty
From: |
Christian Borntraeger |
Subject: |
[Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty |
Date: |
Thu, 29 Dec 2011 13:47:43 +0100 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.24) Gecko/20111108 Lightning/1.0b2 Thunderbird/3.1.16 |
From: Christian Borntraeger <address@hidden>
when I tried qemu with -virtio-console pty the guest hangs and attaching on
/dev/pts/<x> does
not return anything if the attachement is too late.
Turns out that the console is already throttled and the guest is heavily
spinning but get_buf
never returns the buffer. There seems to be no way for the console to
unthrottle the port.
For the virtio-serial use case we dont want to loose data but for the console
case we better
drop data instead of "killing" the guest console. If we get chardev->frontend
notification
and a better behaving virtio-console we can revert this fix.
Signed-off-by: Christian Borntraeger <address@hidden>
---
hw/virtio-serial-bus.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
Index: b/hw/virtio-serial-bus.c
===================================================================
--- a/hw/virtio-serial-bus.c
+++ b/hw/virtio-serial-bus.c
@@ -163,7 +163,19 @@ static void do_flush_queued_data(VirtIOS
abort();
}
if (ret == -EAGAIN || (ret >= 0 && ret < buf_size)) {
- virtio_serial_throttle_port(port, true);
+ /*
+ * this is a temporary check until chardevs can signal to
+ * frontends that they are writable again. This prevents
+ * the console from going into throttled mode (forever)
+ * if virtio-console is connected to a pty without a
+ * listener. Otherwise the guest spins forever.
+ * We can revert this if
+ * 1: chardevs can notify frondends
+ * 2: the guest driver does not spin in these cases
+ */
+ if (!info->is_console) {
+ virtio_serial_throttle_port(port, true);
+ }
port->iov_idx = i;
if (ret > 0) {
port->iov_offset += ret;
- [Qemu-devel] [RFC] virtio-console fails on unconnected pty, Christian Borntraeger, 2011/12/15
- Re: [Qemu-devel] [RFC] virtio-console fails on unconnected pty, Amit Shah, 2011/12/16
- [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty,
Christian Borntraeger <=
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Amit Shah, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Amit Shah, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Christian Borntraeger, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Christian Borntraeger, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Amit Shah, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Christian Borntraeger, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Amit Shah, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Christian Borntraeger, 2011/12/29
- Re: [Qemu-devel] [PATCHv2] Fix virtio-console failure on unconnected pty, Amit Shah, 2011/12/29