On Mon, Jan 11, 2010 at 04:40:14PM +0100, Hannes Reinecke wrote:
Konrad Rzeszutek Wilk wrote:
b) Or utilize xen-detect and load the appropiate modules if we are
running in Xen PV land. The second is by far much simpler but I don't
know if more appropiate. I am attaching an example patch to demonstrate
what I had in mind. (Caveat: I didn't include the pre-requisite for
xen-tools yet).
c). Another way? Any ideas would be much appreciated.
I would favor "modalias" files in /sys, which will be used to modprobe
the modules with the modalias.
Have a look at this:
$ find /sys -name modalias
I think I did not explain the problem quite well. The modalias values
appear after the modules have been loaded. I am at the situation where I am
trying to figure out if I should load the modules or not - so the modalias
values are not present.
D'oh.
But that's exactly the wrong way round.
The sole reason for having a modalias attribute (in the device) is to facilitate
module autoloading.
If the modalias attribute appears _after_ the module has been loaded you might
want to redesign the module ...
Actually the whole module directory appears _after_ the module is
loaded.
The one option that exists right now to detect whether we are running
under Xen is to use 'xen-detect', which I think you are OK with?
I am sure this could be automated in the kernel without the need of extra
special xen handling with scripts.
+xen-detect
+RC=$?
+if [ "$RC" = "1" ] ; then
why not?
if xen-detect ; then ...; fi
Ooh, the patches I've for xen-detect return three different return values.
1 for PV Xen, 2 for HVM Xen, and 0 if no Xen.
Also xen-detect prints this out (depending on the scenario):
Running in HVM context on Xen v4.0.
Running in PV context on Xen v4.0.
Not running on Xen.
And it looks that 'if xen-detect', the if clause takes under consideration
the output - which means that on machines not running Xen it would still jump in the
"then" clause.
"if xen-detect" looks at the return code of xen-detect
so it should be
if ! xen-detect; then echo we are running xen;else echo no xen;done
I think I am going to modify the xen-detect to accept another flag that would
just print a string if it is running in a PV context and nothing else- that
should make it easier.
Please don't. return code are much better to parse than text strings
Easiest bit would be if there were some bits of (virtual) devices, to which the Xen
drivers could attach to. Doesn't Xen already provide something here?
What does xen-detect do?
If it's just looking at some sysfs attributes then we can easily build up a udev rule.
--
Luca Berra -- bluca@xxxxxxxxxx
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