KVM: arm64: nv: Properly check ESR_EL2.VNCR on taking a VNCR_EL2 related fault

Instead of checking for the ESR_EL2.VNCR bit being set (the only case
we should be here), we are actually testing random bits in ESR_EL2.DFSC.

13 obviously being a lucky number, it matches both permission and
translation fault status codes, which explains why we never saw it
failing. This was found by inspection, while reviewing a vaguely
related patch.

Whilst we're at it, turn the BUG_ON() into a WARN_ON_ONCE(), as
exploding here is just silly.

Fixes: 069a05e ("KVM: arm64: nv: Handle VNCR_EL2-triggered faults")
Signed-off-by: Marc Zyngier <[email protected]>
Reviewed-by: Joey Gouly <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Oliver Upton <[email protected]>

Author: Marc Zyngier

arch/arm64/kvm/nested.c

@@ -1287,7 +1287,7 @@ int kvm_handle_vncr_abort(struct kvm_vcpu *vcpu)
 	struct vncr_tlb *vt = vcpu->arch.vncr_tlb;
 	u64 esr = kvm_vcpu_get_esr(vcpu);
 
-	BUG_ON(!(esr & ESR_ELx_VNCR_SHIFT));
+	WARN_ON_ONCE(!(esr & ESR_ELx_VNCR));
 
 	if (esr_fsc_is_permission_fault(esr)) {
 		inject_vncr_perm(vcpu);