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From: Charles Duffy <cduffy@spamcop.net>
Date: Thu, 02 Aug 2007 20:48:10 -0500
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Subject: [Qemu-devel] Re: Network connections stalling
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To: qemu-devel@nongnu.org

This loss of connectivity is still happening; at least within my
environment, it's quite reproducible. While I've eliminated the message
about being unable to set the RTC to 1024Hz by recompiling my host
kernel without CONFIG_HPET_RTC_IRQ, the host's kernel is frequently
complaining "rtc: lost some interrupts at 1024Hz".

I'm using tap-based networking (-net nic -net
tap,ifname=tap0,script=./tap0-start), where tap0 is bridged to my local
ethernet device, and outgoing network traffic from the qemu instance is
visible if I monitor traffic on the bridge.

Indeed, external responses to such traffic (ie. ARP responses) are
visible on the bridge, but evidently not to the virtual machine: the TX
counter rises when I try to ping the outside world, but the RX counter
does not. Resetting the device (ifconfig eth0 down; ifconfig eth0 up)
brings it back alive -- but this isn't an action which can trivially be
slotted into a trivial, single-threaded install script.

These same scripts have been tested on real hardware, and have not
turned up this issue. Certainly, a race condition unrelated to qemu is
possible, but I'd appreciate any insight 'yall can provide. Thank you!