[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] debugging hypervisor console I/O
> > If you have a guest you are just booting with no console I/O device for > xen in the guest, I assume that HYPERVISOR_console_io(0, "HI!\n", 4) > > will get some console I/O down to xen, right? And that xen will arrange > for the console I/o to appear on port, e.g., 9611 if I have set the > console_port to 9611 in /etc/xc/defaults. Not quite. HYPERVISOR_console_io is intended for input/output over the system serial console. Access is normally restricted to domain 0, but for debug Xen builds anyone can play. > I have a guest that can exit but not do console I/O, and I'm trying to > track down what is missing. The "production" way for guests to generate console output is via the comms ring to domain0 -- there's an example of how to do this in xenolinux-sparse/arch/xen/drivers/console/console.c The mechanism is slightly complicated, so for start of day debugging you're better off using HYPERVISOR_console_io to the serial port. Xen versions up until 1.2 used to have what was known as the "domain UDP console" which took HYPERVISOR_console_write calls and generated a fake UDP packet containing the message that was then delivered to domain 0 via inter-VM networking; A UDP client in domain 0 displayed the message. Although this mechanism was nice and simple, it was output-only and had potential denial of service vulnerabilities for untrusted guests generating large amounts of output. The new comms ring mechanism is progress, but not great for bringing up a new guest OS. Any kind of development on Xen is much easier with a serial line anyhow -- you can use ^A^A^A to switch to Xen's debug interface which has a few useful features (and is trivial to add more). Hit 'h' for help. The most useful keys are 'd','p','q' and 'R' to reboot. > What's a reasonable starting point to debug a lack of console I/O? debug > print in Xen for domains > 0? Plumb your VMWare serial port through to a telnet terminal on the host OS. BTW: It would be really great if you could keep a few notes as you go so that we could compile a 'guest os porting howto'. Cheers, Ian ------------------------------------------------------- This SF.Net email is sponsored by: Oracle 10g Get certified on the hottest thing ever to hit the market... Oracle 10g. Take an Oracle 10g class now, and we'll give you the exam FREE. http://ads.osdn.com/?ad_id=3149&alloc_id=8166&op=click _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
|
![]() |
Lists.xenproject.org is hosted with RackSpace, monitoring our |