ARM: KVM: fix unbalanced get_cpu() in access_dcsw

In the very unlikely event where a guest would be foolish enough to
*read* from a write-only cache maintainance register, we end up
with preemption disabled, due to a misplaced get_cpu().

Just move the "is_write" test outside of the critical section.
Signed-off-by: NMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: NChristoffer Dall <cdall@cs.columbia.edu>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/arm/kvm/coproc.c

@@ -79,11 +79,11 @@ static bool access_dcsw(struct kvm_vcpu *vcpu,
 	u32 val;
 	int cpu;
 
-	cpu = get_cpu();
-
 	if (!p->is_write)
 		return read_from_write_only(vcpu, p);
 
+	cpu = get_cpu();
+
 	cpumask_setall(&vcpu->arch.require_dcache_flush);
 	cpumask_clear_cpu(cpu, &vcpu->arch.require_dcache_flush);