Carsten Emde wrote: > Avi Kivity wrote: >> David Brown wrote: >>> I thought I'd try out the realtime patch set and it didn't work at all >>> with kvm. The console didn't dump anything and the system completely >>> locked up. > Up to now, the unmodified kvm module never worked with any RT kernel. > This would only change, if RT patched kernels were routinely used in the > kvm release tests which is, for the time being, not the case.
As far as I understood (but didn't re-test yet), latest kvm release does include all features required to run over -rt. This was at least the case for kvm-git I picked up last week and merged into 2.6.23-rt1. The only issue is that out-of-tree kvm doesn't enable the preemption notifiers (maybe there were one or two further minor issues, I think to recall missing smp_ops exports being one, but these were not -rt related). > > However, tglx once provided a hand-crafted kvm version that can be used > together with a selected RT kernel -> see "Latest Stable" > (http://www.osadl.org/Latest-Stable.latest-stable-realtime-kernel.0.html) > realtime kernel. It is based on kernel 2.6.21.6-rt21 and kvm-28. > > We used these modules to carry out a number of "proof of concept" tests > which were very successful. The realtime capabilities of the host system > remained unchanged irrespective of whether the kvm guest system (no > graphics) was running or not. This was even the case while the guest > system was booting. Interesting result - you've read about the wbinvd issues? Is there no wbinvd in the bios shipped with older kvm? Which VM extension did you test, both Intel and AMD? I would bet that your X issues are due to the same effect. X startup/shutdown involves a lot of wbinvd calls on my test boxes. To sum up my findings: kvm over whatever RT kernel is risky (latency-wise) unless you can audit or even para-virtualise your guest OS /wrt wbinvd. Maybe we can discuss this also in Linz by the end of the week. :) Jan -- Siemens AG, Corporate Technology, CT SE 2 Corporate Competence Center Embedded Linux - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
