[Qemu-devel] Re: 8139cp problems - steps to reproduce

[Nikola Ciprich <extmaillist@linuxbox.cz>]

Well, so with e1000, the problem comes much faster, probably already after few hundreds of MB
n.

On Mon, Sep 08, 2008 at 09:57:59AM +0200, Nikola Ciprich wrote:
> Hello Avi and everybody,
> 
> (and in advance, sorry for cross-posting).
> 
> As it was already reported, some people (including me :)) have problems
> with network getting stuck from time to time in KVM guests. 
> 
> According to http://qemu-forum.ipi.fi/viewtopic.php?f=4&t=4563&start=0&st=0&sk=t&sd=a&sid=fcf252234991e017919ca7d0eb3799a3
> the problem is maybe not KVM speciffic.
> 
> I can confirm that the problem seems to be occuring after transmitting few gigabytes of data,
> so it can be simply reproduced by starting KVM guest, mounting some NFS in it, and then
> starting shell loop dd if=/mnt/nfs/bigimage.iso of=/dev/zero
> after some runs (in my case usually tens of GB), the problem occurs:
> [ 2159.614496] NETDEV WATCHDOG: eth0: transmit timed out
> [ 2159.614537] eth0: Transmit timeout, status  d   2b   15 80ff
> 
> The status "  d   2b   15 80ff" is always the same, on all testing machines
> which according to 8139cp.c means
> 
> Command register=d
> C+ command register=2b
> Interrupt status=15
> Interrupt mask=80ff
> 
> Particular bits are explained in 8139cp comments, unfortunately this didn't make me any smarter :(. 
> The only thing I tried was disabling rx/tx checksumming for the interface (this was needed
> fox XEN domUs as well), but it didn't helped.
> 
> What is important to note is, that this is simply reproducible this way for x86_32 guests (I'm
> using x86_64 host). For x86_64 guests, the problem is actually much WORSE, as it usually gets
> host machine into totally unusable state (it replies to pings, but that's all, no message in logs
> after reboot, etc). I'll try to investigate it further.
> 
> Another important note is, that the problem is certainly NOT system-load related, it
> occurs even when the machine is idle (except from load caused by network dd)
> 
> I'm using kvm-74 now, with 2.6.26 host and 2.6.24 guest, and bridged networking.
> 
> I'll try using e1000 driver, but I think that 8139cp is ATM considered the most stable choice, right?
> 
> So does somebody have an idea on where the problem could be? Of course I'll be glad to (try) to help
> debugging...
> 
> Thanks a lot in advance!
> 
> nik
> 
> 
> -- 
> -------------------------------------
> Nikola CIPRICH
> LinuxBox.cz, s.r.o.
> 28. rijna 168, 709 01 Ostrava
> 
> tel.:   +420 596 603 142
> fax:    +420 596 621 273
> mobil:  +420 777 093 799
> www.linuxbox.cz
> 
> mobil servis: +420 737 238 656
> email servis: servis@linuxbox.cz
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-- 
-------------------------------------
Nikola CIPRICH
LinuxBox.cz, s.r.o.
28. rijna 168, 709 01 Ostrava

tel.:   +420 596 603 142
fax:    +420 596 621 273
mobil:  +420 777 093 799
www.linuxbox.cz

mobil servis: +420 737 238 656
email servis: servis@linuxbox.cz
-------------------------------------