On Tue, 2007-10-23 at 10:35 +0200, Jan Kiszka wrote: > Sven-Thorsten Dietrich wrote: > > On Mon, 2007-10-22 at 09:01 +0200, Back, Michael (ext) wrote: > >> Hallo, > >> I tried to run Windows XP with KVM on Linux 2.6.31.1 on a > > > > You mean .21.1 ? > > Classic typo I interestingly also did several times the last week. :) > > > > >> AMD Opteron and on a Intel Xeon, on both it works fine! > > > >> After this test I patch the kernel with the current prempt-patch and on > >> both it doesn't works! > > > > Did you try against 2.6.23-rt1. > > kvm in -rt1 is not usable. It's too old, lacking PREEMPT_NOTIFIER > support, thus quickly triggering lockdep. > > > > > If you must stay on .21, you might have some other issues with the AMD > > and NUMA. > > > > At the very least, you will need to apply the attached patch from git > > somehow, although this patch is against a new scheduler post 2.6.22, so > > good luck :) > > <--snip--> > > Those patches are already mainline... :-> > > What you rather need are latest kvm patches, or - if building the kvm > distribution out of tree - a patch to enabled CONFIG_PREEMPT_NOTIFIERS > unconditionally: > > --- linux-2.6.23.1-rt/kernel/Kconfig.preempt.orig > +++ linux-2.6.23.1-rt/kernel/Kconfig.preempt > @@ -136,6 +136,7 @@ > > config PREEMPT_NOTIFIERS > bool > + default y > > config PREEMPT_BKL > bool > > > Still, I'm seeing oopses here (more precisely, lock validator > complaints), but I need to re-test, better using kvm from git instead of > kvm-48. > > Beyond this, I'm struggling to understand 300-400 us vm-exit latencies > (over Intel VMX), which appear to be independent of the underlying > system. See kvm-devel. Such latencies would limit the RT usability of > kvm - unless you spent dedicated CPUs. Some work is still left to be done in this area. Until then you will see problems like you are describing. At one point I had a patch series that allowed KVM to actually work in -rt without crashes, and with decent latencies (both host, and guest). Some point soon I will revive the series and port it to the latest kvm.git. HTH Regards, -Greg
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