On Tue, Dec 22, 2009 at 03:28:47PM +0100, Harald Hoyer wrote: > On 12/21/2009 10:26 PM, Konrad Rzeszutek Wilk wrote: >> Hey Harald and initramfs mailing list, >> >> I am working on de-coupling a lot of Xen modules from the PV-OPS >> kernel (git://git.kernel.org/pub/scm/linux/kernel/git/jeremy/xen.git) >> so that it is not neccessary to have them compiled in. >> >> I've gotten to the point that all of the drivers (fbfront, kbdfront, >> netfront, blkfront, pcifront) can be loaded on demand. Some of them >> can't be unloaded (still working on that). >> >> The next stage is to make the loading automatic, and detect if the kernel >> is running under Xen (PV) and if so load the neccesssary modules. >> >> To solve that, my thought was to: >> >> a) Write udev rules that would be act up if the kernel emitted such >> rules. But the kernel does not emit any uevents for this purpose and >> it does not emit any virtualization ones until the virtualization modules >> are loaded. I could write up code that would emit this >> information and be generic enough that it would do so for anything >> that uses the paravirt strutures. So basically a SysFS interface for >> the paravirt interface. >> >> 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. 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. 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. -- To unsubscribe from this list: send the line "unsubscribe initramfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
