KVM: arm64: Warn when PENDING_EXCEPTION and INCREMENT_PC are set together

We really don't want PENDING_EXCEPTION and INCREMENT_PC to ever be
set at the same time, as they are mutually exclusive. Add checks
that will generate a warning should this ever happen.
Reviewed-by: Fuad Tabba <tabba@google.com>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/include/asm/kvm_emulate.h

@@ -473,11 +473,13 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
 
 static __always_inline void kvm_incr_pc(struct kvm_vcpu *vcpu)
 {
+	WARN_ON(vcpu_get_flag(vcpu, PENDING_EXCEPTION));
 	vcpu_set_flag(vcpu, INCREMENT_PC);
 }
 
 #define kvm_pend_exception(v, e)					\
 	do {								\
+		WARN_ON(vcpu_get_flag((v), INCREMENT_PC));		\
 		vcpu_set_flag((v), PENDING_EXCEPTION);			\
 		vcpu_set_flag((v), e);					\
 	} while (0)