[PATCH v4 18/43] KVM: arm64: Handle trapping of FEAT_LS64* instructions

[Marc Zyngier <maz@kernel.org>]

We generally don't expect FEAT_LS64* instructions to trap, unless
they are trapped by a guest hypervisor.

Otherwise, this is just the guest playing tricks on us by using
an instruction that isn't advertised, which we handle with a well
deserved UNDEF.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/kvm/handle_exit.c | 56 ++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index b73dc26bc44b4..ff75695fb8c96 100644
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -298,6 +298,61 @@ static int handle_svc(struct kvm_vcpu *vcpu)
 	return 1;
 }
 
+static int handle_other(struct kvm_vcpu *vcpu)
+{
+	bool is_l2 = vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu);
+	u64 hcrx = __vcpu_sys_reg(vcpu, HCRX_EL2);
+	u64 esr = kvm_vcpu_get_esr(vcpu);
+	u64 iss = ESR_ELx_ISS(esr);
+	struct kvm *kvm = vcpu->kvm;
+	bool allowed, fwd = false;
+
+	/*
+	 * We only trap for two reasons:
+	 *
+	 * - the feature is disabled, and the only outcome is to
+	 *   generate an UNDEF.
+	 *
+	 * - the feature is enabled, but a NV guest wants to trap the
+	 *   feature used by its L2 guest. We forward the exception in
+	 *   this case.
+	 *
+	 * What we don't expect is to end-up here if the guest is
+	 * expected be be able to directly use the feature, hence the
+	 * WARN_ON below.
+	 */
+	switch (iss) {
+	case ESR_ELx_ISS_OTHER_ST64BV:
+		allowed = kvm_has_feat(kvm, ID_AA64ISAR1_EL1, LS64, LS64_V);
+		if (is_l2)
+			fwd = !(hcrx & HCRX_EL2_EnASR);
+		break;
+	case ESR_ELx_ISS_OTHER_ST64BV0:
+		allowed = kvm_has_feat(kvm, ID_AA64ISAR1_EL1, LS64, LS64_ACCDATA);
+		if (is_l2)
+			fwd = !(hcrx & HCRX_EL2_EnAS0);
+		break;
+	case ESR_ELx_ISS_OTHER_LDST64B:
+		allowed = kvm_has_feat(kvm, ID_AA64ISAR1_EL1, LS64, LS64);
+		if (is_l2)
+			fwd = !(hcrx & HCRX_EL2_EnALS);
+		break;
+	default:
+		/* Clearly, we're missing something. */
+		WARN_ON_ONCE(1);
+		allowed = false;
+	}
+
+	WARN_ON_ONCE(allowed && !fwd);
+
+	if (allowed && fwd)
+		kvm_inject_nested_sync(vcpu, esr);
+	else
+		kvm_inject_undefined(vcpu);
+
+	return 1;
+}
+
 static exit_handle_fn arm_exit_handlers[] = {
 	[0 ... ESR_ELx_EC_MAX]	= kvm_handle_unknown_ec,
 	[ESR_ELx_EC_WFx]	= kvm_handle_wfx,
@@ -307,6 +362,7 @@ static exit_handle_fn arm_exit_handlers[] = {
 	[ESR_ELx_EC_CP14_LS]	= kvm_handle_cp14_load_store,
 	[ESR_ELx_EC_CP10_ID]	= kvm_handle_cp10_id,
 	[ESR_ELx_EC_CP14_64]	= kvm_handle_cp14_64,
+	[ESR_ELx_EC_OTHER]	= handle_other,
 	[ESR_ELx_EC_HVC32]	= handle_hvc,
 	[ESR_ELx_EC_SMC32]	= handle_smc,
 	[ESR_ELx_EC_HVC64]	= handle_hvc,
-- 
2.39.2