KVM: arm64: Use the in-context stage-1 in __kvm_find_s1_desc_level()

Running the external_aborts selftest at EL2 leads to an ugly splat due
to the stage-1 MMU being disabled for the walked context, owing to the
fact that __kvm_find_s1_desc_level() is hardcoded to the EL1&0 regime.

Select the appropriate translation regime for the stage-1 walk based on
the current vCPU context.

Fixes: b8e625167a32 ("KVM: arm64: Add S1 IPA to page table level walker")
Signed-off-by: Oliver Upton <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>

arch/arm64/kvm/at.c

···
 			.fn	= match_s1_desc,
 			.priv	= &dm,
 		},
-		.regime	= TR_EL10,
 		.as_el0	= false,
 		.pan	= false,
 	};
 	struct s1_walk_result wr = {};
 	int ret;
+
+	if (is_hyp_ctxt(vcpu))
+		wi.regime = vcpu_el2_e2h_is_set(vcpu) ? TR_EL20 : TR_EL2;
+	else
+		wi.regime = TR_EL10;
 
 	ret = setup_s1_walk(vcpu, &wi, &wr, va);
 	if (ret)