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 <[email protected]>

Acked-by Lorenzo Pieralisi <[email protected]>

Acked-by Marc Zyngier <[email protected]>

Signed-off-by Christoffer Dall <[email protected]>

Signed-off-by Shannon Zhao <[email protected]>

Signed-off-by Greg Kroah-Hartman <[email protected]>

---
 arch/arm/kvm/arm.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

arch/arm/kvm/arm.c +2 -1

@@ -825,7 +825,8 @@ static int hyp_init_cpu_notify(struct no
 	switch (action) {
 	case CPU_STARTING:
 	case CPU_STARTING_FROZEN:
-		cpu_init_hyp_mode(NULL);
+		if (__hyp_get_vectors() == hyp_default_vectors)
+			cpu_init_hyp_mode(NULL);
 		break;
 	}

Patches currently in stable-queue which might be from [email protected] are

queue-3.14/arm-kvm-fix-cpu-hotplug.patch