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: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/arm/kvm/coproc.c b/arch/arm/kvm/coproc.c
index 4ea9a98..7bed755 100644 (file)
--- a/arch/arm/kvm/coproc.c
+++ b/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);