1 files changed, 25 insertions, 4 deletions

diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index e1a30d1bcd06..b072098ee44e 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -20,6 +20,9 @@ enum trap_behaviour {
 	BEHAVE_FORWARD_READ	= BIT(0),
 	BEHAVE_FORWARD_WRITE	= BIT(1),
 	BEHAVE_FORWARD_RW	= BEHAVE_FORWARD_READ | BEHAVE_FORWARD_WRITE,
+
+	/* Traps that take effect in Host EL0, this is rare! */
+	BEHAVE_FORWARD_IN_HOST_EL0	= BIT(2),
 };
 
 struct trap_bits {
@@ -2128,11 +2131,19 @@ static u64 kvm_get_sysreg_res0(struct kvm *kvm, enum vcpu_sysreg sr)
 	return masks->mask[sr - __VNCR_START__].res0;
 }
 
-static bool check_fgt_bit(struct kvm *kvm, bool is_read,
+static bool check_fgt_bit(struct kvm_vcpu *vcpu, bool is_read,
 			  u64 val, const union trap_config tc)
 {
+	struct kvm *kvm = vcpu->kvm;
 	enum vcpu_sysreg sr;
 
+	/*
+	 * KVM doesn't know about any FGTs that apply to the host, and hopefully
+	 * that'll remain the case.
+	 */
+	if (is_hyp_ctxt(vcpu))
+		return false;
+
 	if (tc.pol)
 		return (val & BIT(tc.bit));
 
@@ -2209,7 +2220,15 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
 	 * If we're not nesting, immediately return to the caller, with the
 	 * sysreg index, should we have it.
 	 */
-	if (!vcpu_has_nv(vcpu) || is_hyp_ctxt(vcpu))
+	if (!vcpu_has_nv(vcpu))
+		goto local;
+
+	/*
+	 * There are a few traps that take effect InHost, but are constrained
+	 * to EL0. Don't bother with computing the trap behaviour if the vCPU
+	 * isn't in EL0.
+	 */
+	if (is_hyp_ctxt(vcpu) && !vcpu_is_host_el0(vcpu))
 		goto local;
 
 	switch ((enum fgt_group_id)tc.fgt) {
@@ -2255,12 +2274,14 @@ bool triage_sysreg_trap(struct kvm_vcpu *vcpu, int *sr_index)
 		goto local;
 	}
 
-	if (tc.fgt != __NO_FGT_GROUP__ && check_fgt_bit(vcpu->kvm, is_read,
-							val, tc))
+	if (tc.fgt != __NO_FGT_GROUP__ && check_fgt_bit(vcpu, is_read, val, tc))
 		goto inject;
 
 	b = compute_trap_behaviour(vcpu, tc);
 
+	if (!(b & BEHAVE_FORWARD_IN_HOST_EL0) && vcpu_is_host_el0(vcpu))
+		goto local;
+
 	if (((b & BEHAVE_FORWARD_READ) && is_read) ||
 	    ((b & BEHAVE_FORWARD_WRITE) && !is_read))
 		goto inject;