KVM: arm64: Enable FP8 support when available and configured

If userspace has enabled FP8 support (by setting ID_AA64PFR2_EL1.FPMR
to 1), let's enable the feature by setting HCRX_EL2.EnFPM for the vcpu.
Reviewed-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20240820131802.3547589-8-maz@kernel.orgSigned-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/sys_regs.c

@@ -4579,6 +4579,9 @@ void kvm_calculate_traps(struct kvm_vcpu *vcpu)
 
 		if (kvm_has_feat(kvm, ID_AA64MMFR3_EL1, TCRX, IMP))
 			vcpu->arch.hcrx_el2 |= HCRX_EL2_TCR2En;
+
+		if (kvm_has_fpmr(kvm))
+			vcpu->arch.hcrx_el2 |= HCRX_EL2_EnFPM;
 	}
 
 	if (test_bit(KVM_ARCH_FLAG_FGU_INITIALIZED, &kvm->arch.flags))