KVM: arm64: Add standard hypervisor firmware register

Introduce the firmware register to hold the standard hypervisor
service calls (owner value 5) as a bitmap. The bitmap represents
the features that'll be enabled for the guest, as configured by
the user-space. Currently, this includes support only for
Paravirtualized time, represented by bit-0.
Signed-off-by: Raghavendra Rao Ananta <rananta@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
[maz: tidy-up bitmap values]
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220502233853.1233742-4-rananta@google.com

arch/arm64/include/asm/kvm_host.h

@@ -105,9 +105,11 @@ struct kvm_arch_memory_slot {
  * struct kvm_smccc_features: Descriptor of the hypercall services exposed to the guests
  *
  * @std_bmap: Bitmap of standard secure service calls
+ * @std_hyp_bmap: Bitmap of standard hypervisor service calls
  */
 struct kvm_smccc_features {
 	unsigned long std_bmap;
+	unsigned long std_hyp_bmap;
 };
 
 struct kvm_arch {

arch/arm64/include/uapi/asm/kvm.h

@@ -345,6 +345,13 @@ enum {
 	KVM_REG_ARM_STD_BMAP_BIT_COUNT,
 };
 
+#define KVM_REG_ARM_STD_HYP_BMAP		KVM_REG_ARM_FW_FEAT_BMAP_REG(1)
+
+enum {
+	KVM_REG_ARM_STD_HYP_BIT_PV_TIME	= 0,
+	KVM_REG_ARM_STD_HYP_BMAP_BIT_COUNT,
+};
+
 /* Device Control API: ARM VGIC */
 #define KVM_DEV_ARM_VGIC_GRP_ADDR	0
 #define KVM_DEV_ARM_VGIC_GRP_DIST_REGS	1

arch/arm64/kvm/hypercalls.c

@@ -11,6 +11,8 @@
 
 #define KVM_ARM_SMCCC_STD_FEATURES				\
 	GENMASK(KVM_REG_ARM_STD_BMAP_BIT_COUNT - 1, 0)
+#define KVM_ARM_SMCCC_STD_HYP_FEATURES				\
+	GENMASK(KVM_REG_ARM_STD_HYP_BMAP_BIT_COUNT - 1, 0)
 
 static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
 {
@@ -71,8 +73,6 @@ static bool kvm_hvc_call_default_allowed(u32 func_id)
 	 */
 	case ARM_SMCCC_VERSION_FUNC_ID:
 	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
-	case ARM_SMCCC_HV_PV_TIME_FEATURES:
-	case ARM_SMCCC_HV_PV_TIME_ST:
 	case ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID:
 	case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
 	case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
@@ -106,6 +106,10 @@ static bool kvm_hvc_call_allowed(struct kvm_vcpu *vcpu, u32 func_id)
 	case ARM_SMCCC_TRNG_RND64:
 		return test_bit(KVM_REG_ARM_STD_BIT_TRNG_V1_0,
 				&smccc_feat->std_bmap);
+	case ARM_SMCCC_HV_PV_TIME_FEATURES:
+	case ARM_SMCCC_HV_PV_TIME_ST:
+		return test_bit(KVM_REG_ARM_STD_HYP_BIT_PV_TIME,
+				&smccc_feat->std_hyp_bmap);
 	default:
 		return kvm_hvc_call_default_allowed(func_id);
 	}
@@ -113,6 +117,7 @@ static bool kvm_hvc_call_allowed(struct kvm_vcpu *vcpu, u32 func_id)
 
 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 {
+	struct kvm_smccc_features *smccc_feat = &vcpu->kvm->arch.smccc_feat;
 	u32 func_id = smccc_get_function(vcpu);
 	u64 val[4] = {SMCCC_RET_NOT_SUPPORTED};
 	u32 feature;
@@ -176,7 +181,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 			}
 			break;
 		case ARM_SMCCC_HV_PV_TIME_FEATURES:
-			val[0] = SMCCC_RET_SUCCESS;
+			if (test_bit(KVM_REG_ARM_STD_HYP_BIT_PV_TIME,
+				     &smccc_feat->std_hyp_bmap))
+				val[0] = SMCCC_RET_SUCCESS;
 			break;
 		}
 		break;
@@ -222,6 +229,7 @@ static const u64 kvm_arm_fw_reg_ids[] = {
 	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_2,
 	KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_3,
 	KVM_REG_ARM_STD_BMAP,
+	KVM_REG_ARM_STD_HYP_BMAP,
 };
 
 void kvm_arm_init_hypercalls(struct kvm *kvm)
@@ -229,6 +237,7 @@ void kvm_arm_init_hypercalls(struct kvm *kvm)
 	struct kvm_smccc_features *smccc_feat = &kvm->arch.smccc_feat;
 
 	smccc_feat->std_bmap = KVM_ARM_SMCCC_STD_FEATURES;
+	smccc_feat->std_hyp_bmap = KVM_ARM_SMCCC_STD_HYP_FEATURES;
 }
 
 int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
@@ -317,6 +326,9 @@ int kvm_arm_get_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 	case KVM_REG_ARM_STD_BMAP:
 		val = READ_ONCE(smccc_feat->std_bmap);
 		break;
+	case KVM_REG_ARM_STD_HYP_BMAP:
+		val = READ_ONCE(smccc_feat->std_hyp_bmap);
+		break;
 	default:
 		return -ENOENT;
 	}
@@ -339,6 +351,10 @@ static int kvm_arm_set_fw_reg_bmap(struct kvm_vcpu *vcpu, u64 reg_id, u64 val)
 		fw_reg_bmap = &smccc_feat->std_bmap;
 		fw_reg_features = KVM_ARM_SMCCC_STD_FEATURES;
 		break;
+	case KVM_REG_ARM_STD_HYP_BMAP:
+		fw_reg_bmap = &smccc_feat->std_hyp_bmap;
+		fw_reg_features = KVM_ARM_SMCCC_STD_HYP_FEATURES;
+		break;
 	default:
 		return -ENOENT;
 	}
@@ -439,6 +455,7 @@ int kvm_arm_set_fw_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg)
 
 		return 0;
 	case KVM_REG_ARM_STD_BMAP:
+	case KVM_REG_ARM_STD_HYP_BMAP:
 		return kvm_arm_set_fw_reg_bmap(vcpu, reg->id, val);
 	default:
 		return -ENOENT;