[PATCH v2] arm/arm64: KVM: detect CPU reset on CPU_PM_EXIT

[Christoffer Dall]

On Tue, Feb 25, 2014 at 10:00:08AM +0000, Marc Zyngier wrote:
> On 21/02/14 17:12, Christoffer Dall wrote:
> > On Fri, Feb 21, 2014 at 11:46:56AM +0000, Marc Zyngier wrote:
> >> Commit 1fcf7ce0c602 (arm: kvm: implement CPU PM notifier) added
> >> support for CPU power-management, using a cpu_notifier 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 is 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 at andrep.de>
> >> Tested-by: Andre Przywara <osp at andrep.de>
> >> Cc: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> >> Cc: Rob Herring <rob.herring at linaro.org>
> >> Acked-by: Christoffer Dall <christoffer.dall at linaro.org>
> >> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
> > 
> > Thanks!
> > 
> > Looks good.
> 
> Thanks. I'm thinking of pushing this to 3.14 as a fix. Any objection?
> 
Nope, go for it.

-Christoffer