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xen-devel
[Xen-devel] Re: [PATCH] Make explicit message when guest failed to suspe
On Thu, 2011-03-03 at 10:13 +0000, Frank Pan wrote:
> Recent xen uses xenbus to suspend PV-on-HVM guest domain. The related
> code in the xen-unstable tree will fall into infinite loop when guest
> domain failed on suspending one or more devices.
This is a bug in Xend, it should never enter an infinite loop regardless
of guest behaviour. The code certainly appears to expect to be managing
a timeout, perhaps it has bitrotted?
> The patch attached changes the logic, and raises an XendError after 1
> minute waiting. The patch also makes use of "control/shutdown" entry
> in xenstore, allows guest kernel report the failure of the suspending.
I don't think you can change the xenbus protocol in this way without
further rationale regarding it's correctness.
In particular you need to consider and explain how it remains compatible
with a new kernel running on older toolstacks and vice versa.
> Any suggestions?
Perhaps a separate control/shutdown-error key? The message written
should be more verbose than just "failed" if/when more specific
information is available to the kernel.
> @@ -165,6 +165,8 @@ out_destroy_sm:
> stop_machine_destroy();
>
> out:
> + if (cancelled)
> + xenbus_write(XBT_NIL, "control", "shutdown", "failed");
cancelled does not necessarily imply failure, it can mean the suspend
resulted in a checkpoint rather than a full suspend.
Ian.
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