KVM: arm64: hide MOPS from guests

As FEAT_MOPS is not supported in guests yet, hide it from the ID
registers for guests.

The MOPS instructions are UNDEFINED in guests as HCRX_EL2.MSCEn is not
set in HCRX_GUEST_FLAGS, and will take an exception to EL1 if executed.

Signed-off-by: Kristina Martsenko <kristina.martsenko@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <maz@kernel.org>
Acked-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20230509142235.3284028-7-kristina.martsenko@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

arch/arm64/kvm/sys_regs.c

@@ -1252,6 +1252,7 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc const *r
 				 ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_GPA3));
 		if (!cpus_have_final_cap(ARM64_HAS_WFXT))
 			val &= ~ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_WFxT);
+		val &= ~ARM64_FEATURE_MASK(ID_AA64ISAR2_EL1_MOPS);
 		break;
 	case SYS_ID_AA64DFR0_EL1:
 		/* Limit debug to ARMv8.0 */