[PATCH] arm: kvm: fix CPU hotplug

[Christoffer Dall]

On Mon, Sep 22, 2014 at 03:52:48PM +0100, Vladimir Murzin wrote:
> On some platforms with no power management capabilities, the hotplug
> implementation is allowed to return from a smp_ops.cpu_die() call as a
> function return. Upon a CPU onlining event, the KVM CPU notifier tries
> to reinstall the hyp stub, which fails on platform where no reset took
> place following a hotplug event, with the message:
> 
> CPU1: smp_ops.cpu_die() returned, trying to resuscitate
> CPU1: Booted secondary processor
> Kernel panic - not syncing: unexpected prefetch abort in Hyp mode at: 0x80409540
> unexpected data abort in Hyp mode at: 0x80401fe8
> unexpected HVC/SVC trap in Hyp mode at: 0x805c6170
> 
> since KVM code is trying to reinstall the stub on a system where it is
> already configured.
> 
> To prevent this issue, this patch adds a check in the KVM hotplug
> notifier that detects if the HYP stub really needs re-installing when a
> CPU is onlined and skips the installation call if the stub is already in
> place, which means that the CPU has not been reset.
> 
> Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
> Acked-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>

Applied to queue, thanks

-Christoffer