KVM: arm64: Inherit RESx bits from FGT register descriptors

The FGT registers have their computed RESx bits stashed in specific
descriptors, which we can easily use when computing the masks used
for the guest.

This removes a bit of boilerplate code.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Reviewed-by: Fuad Tabba <tabba@google.com>
Tested-by: Fuad Tabba <tabba@google.com>
Link: https://patch.msgid.link/20260202184329.2724080-7-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>

Author: Marc Zyngier

arch/arm64/kvm/config.c

@@ -1342,6 +1342,11 @@ static struct resx compute_reg_resx_bits(struct kvm *kvm,
 	resx = compute_resx_bits(kvm, r->bit_feat_map, r->bit_feat_map_sz,
 				 require, exclude);
 
+	if (r->feat_map.flags & MASKS_POINTER) {
+		resx.res0 |= r->feat_map.masks->res0;
+		resx.res1 |= r->feat_map.masks->res1;
+	}
+
 	tmp = compute_resx_bits(kvm, &r->feat_map, 1, require, exclude);
 
 	resx.res0 |= tmp.res0;
@@ -1422,47 +1427,36 @@ struct resx get_reg_fixed_bits(struct kvm *kvm, enum vcpu_sysreg reg)
 	switch (reg) {
 	case HFGRTR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgrtr_desc, 0, 0);
-		resx.res1 |= HFGRTR_EL2_RES1;
 		break;
 	case HFGWTR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgwtr_desc, 0, 0);
-		resx.res1 |= HFGWTR_EL2_RES1;
 		break;
 	case HFGITR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgitr_desc, 0, 0);
-		resx.res1 |= HFGITR_EL2_RES1;
 		break;
 	case HDFGRTR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hdfgrtr_desc, 0, 0);
-		resx.res1 |= HDFGRTR_EL2_RES1;
 		break;
 	case HDFGWTR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hdfgwtr_desc, 0, 0);
-		resx.res1 |= HDFGWTR_EL2_RES1;
 		break;
 	case HAFGRTR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hafgrtr_desc, 0, 0);
-		resx.res1 |= HAFGRTR_EL2_RES1;
 		break;
 	case HFGRTR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgrtr2_desc, 0, 0);
-		resx.res1 |= HFGRTR2_EL2_RES1;
 		break;
 	case HFGWTR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgwtr2_desc, 0, 0);
-		resx.res1 |= HFGWTR2_EL2_RES1;
 		break;
 	case HFGITR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &hfgitr2_desc, 0, 0);
-		resx.res1 |= HFGITR2_EL2_RES1;
 		break;
 	case HDFGRTR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &hdfgrtr2_desc, 0, 0);
-		resx.res1 |= HDFGRTR2_EL2_RES1;
 		break;
 	case HDFGWTR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &hdfgwtr2_desc, 0, 0);
-		resx.res1 |= HDFGWTR2_EL2_RES1;
 		break;
 	case HCRX_EL2:
 		resx = compute_reg_resx_bits(kvm, &hcrx_desc, 0, 0);