[PATCH 11/17] KVM: arm64: Hide FEAT_NMI from guests

[Jinjie Ruan]

From: Mark Brown <broonie@xxxxxxxxxx>

FEAT_NMI is not yet useful to guests pending implementation of vGIC
support. Mask out the feature from the ID register and prevent guests
creating state in ALLINT.ALLINT by activating the trap on write provided
in HCRX_EL2.TALLINT when they are running. There is no trap available
for reads from ALLINT.

We do not need to check for FEAT_HCRX since it is mandatory since v8.7
and FEAT_NMI is a v8.8 feature.

Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20221112151708.175147-10-broonie@xxxxxxxxxx
Signed-off-by: Jinjie Ruan <ruanjinjie@xxxxxxxxxx>
---
 arch/arm64/kvm/hyp/include/hyp/switch.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/hyp/switch.h b/arch/arm64/kvm/hyp/include/hyp/switch.h
index 18131e395e24..21b19f331a12 100644
--- a/arch/arm64/kvm/hyp/include/hyp/switch.h
+++ b/arch/arm64/kvm/hyp/include/hyp/switch.h
@@ -346,6 +346,9 @@ static inline void __activate_traps_common(struct kvm_vcpu *vcpu)
 		vcpu_set_flag(vcpu, PMUSERENR_ON_CPU);
 	}
 
+	if (cpus_have_final_cap(ARM64_HAS_NMI))
+		sysreg_clear_set_s(SYS_HCRX_EL2, 0, HCRX_EL2_TALLINT);
+
 	if (cpus_have_final_cap(ARM64_HAS_HCX)) {
 		u64 hcrx = vcpu->arch.hcrx_el2;
 		if (is_nested_ctxt(vcpu)) {
@@ -367,6 +370,9 @@ static inline void __deactivate_traps_common(struct kvm_vcpu *vcpu)
 {
 	struct kvm_cpu_context *hctxt = host_data_ptr(host_ctxt);
 
+	if (cpus_have_final_cap(ARM64_HAS_NMI))
+		sysreg_clear_set_s(SYS_HCRX_EL2, HCRX_EL2_TALLINT, 0);
+
 	write_sysreg(0, hstr_el2);
 	if (system_supports_pmuv3()) {
 		write_sysreg(ctxt_sys_reg(hctxt, PMUSERENR_EL0), pmuserenr_el0);
-- 
2.34.1