KVM: arm64: Use kvm_has_feat() to check if FEAT_SSBS is advertised to the guest

Currently KVM use cpus_have_final_cap() to check if FEAT_SSBS is
advertised to the guest. But if FEAT_SSBS is writable and isn't
advertised to the guest, this is wrong.

Update it to use kvm_has_feat() to check if FEAT_SSBS is advertised
to the guest, thus the KVM can do the right thing if FEAT_SSBS isn't
advertised to the guest.
Signed-off-by: Shaoqin Huang <shahuang@redhat.com>
Link: https://lore.kernel.org/r/20240723072004.1470688-3-shahuang@redhat.comSigned-off-by: Marc Zyngier <maz@kernel.org>

arch/arm64/kvm/hypercalls.c

@@ -317,7 +317,7 @@ int kvm_smccc_call_handler(struct kvm_vcpu *vcpu)
 				 * to the guest, and hide SSBS so that the
 				 * guest stays protected.
 				 */
-				if (cpus_have_final_cap(ARM64_SSBS))
+				if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
 					break;
 				fallthrough;
 			case SPECTRE_UNAFFECTED:
@@ -428,7 +428,7 @@ int kvm_arm_copy_fw_reg_indices(struct kvm_vcpu *vcpu, u64 __user *uindices)
  * Convert the workaround level into an easy-to-compare number, where higher
  * values mean better protection.
  */
-static int get_kernel_wa_level(u64 regid)
+static int get_kernel_wa_level(struct kvm_vcpu *vcpu, u64 regid)
 {
 	switch (regid) {
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
@@ -449,7 +449,7 @@ static int get_kernel_wa_level(u64 regid)
 			 * don't have any FW mitigation if SSBS is there at
 			 * all times.
 			 */
-			if (cpus_have_final_cap(ARM64_SSBS))
+			if (kvm_has_feat(vcpu->kvm, ID_AA64PFR1_EL1, SSBS, IMP))
 				return KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2_NOT_AVAIL;
 			fallthrough;
 		case SPECTRE_UNAFFECTED:
@@ -486,7 +486,7 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1:
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2:
 	case KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3:
-		val = get_kernel_wa_level(reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
+		val = get_kernel_wa_level(vcpu, reg->id) & KVM_REG_FEATURE_LEVEL_MASK;
 		break;
 	case KVM_REG_ARM_STD_BMAP:
 		val = READ_ONCE(smccc_feat->std_bmap);
@@ -588,7 +588,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 		if (val & ~KVM_REG_FEATURE_LEVEL_MASK)
 			return -EINVAL;
 
-		if (get_kernel_wa_level(reg->id) < val)
+		if (get_kernel_wa_level(vcpu, reg->id) < val)
 			return -EINVAL;
 
 		return 0;
@@ -624,7 +624,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 		 * We can deal with NOT_AVAIL on NOT_REQUIRED, but not the
 		 * other way around.
 		 */
-		if (get_kernel_wa_level(reg->id) < wa_level)
+		if (get_kernel_wa_level(vcpu, reg->id) < wa_level)
 			return -EINVAL;
 
 		return 0;