On 20/02/14 22:35, Andre Przywara wrote: > On Thu, 20 Feb 2014 15:26:54 +0000 > Marc Zyngier <marc.zyngier@xxxxxxx> wrote: > >> Commit 1fcf7ce0c602 (arm: kvm: implement CPU PM notifier) added >> support for CPU power-management, using a cpu_nofigier to re-init >> KVM on a CPU that entered CPU idle. >> >> The code assumed that a CPU entering idle would actually be powered >> off, loosing its state entierely, and would then need to be >> reinitialized. It turns out that this is not always the case, and >> some HW performs CPU PM without actually killing the core. In this >> case, we try to reinitialize KVM while it still live. It ends up >> badly, as reported by Andre Przywara (using a Calxeda Midway): >> >> [ 3.663897] Kernel panic - not syncing: unexpected prefetch abort >> in Hyp mode at: 0x685760 [ 3.663897] unexpected data abort in Hyp >> mode at: 0xc067d150 [ 3.663897] unexpected HVC/SVC trap in Hyp >> mode at: 0xc0901dd0 >> >> The trick here is to detect if we've been through a full re-init or >> not by looking at HVBAR (VBAR_EL2 on arm64). This involves >> implementing the backend for __hyp_get_vectors in the main KVM HYP >> code (rather small), and checking the return value against the >> default one when the CPU notifier is called on CPU_PM_EXIT. >> >> Reported-by: Andre Przywara <osp@xxxxxxxxx> >> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> >> Cc: Rob Herring <rob.herring@xxxxxxxxxx> >> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx> > > Tested-by: Andre Przywara <osp@xxxxxxxxx> Thanks! > (there seems to be a typo in the second line of the commit message) Ah, good katsh! ;-) > Marc, > > thanks a lot for this quick and perfectly working patch! I still > believe it is actually the firmware that needs to be fixed, but this is > rather unlikely in this special case ... Well, that is completely debatable. This is a valid (if minimal) implementation of cpu idle, and the KVM code *must* be robust enough to deal with that kind of implementation. Cheers, M. -- Jazz is not dead. It just smells funny... _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/cucslists/listinfo/kvmarm
