KVM: x86: Make Hyper-V emulation optional

Hyper-V emulation in KVM is a fairly big chunk and in some cases it may be
desirable to not compile it in to reduce module sizes as well as the attack
surface. Introduce CONFIG_KVM_HYPERV option to make it possible.

Note, there's room for further nVMX/nSVM code optimizations when
!CONFIG_KVM_HYPERV, this will be done in follow-up patches.

Reorganize Makefile a bit so all CONFIG_HYPERV and CONFIG_KVM_HYPERV files
are grouped together.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Tested-by: Jeremi Piotrowski <jpiotrowski@linux.microsoft.com>
Link: https://lore.kernel.org/r/20231205103630.1391318-13-vkuznets@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

1 files changed, 45 insertions, 17 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 81224b9676d9..598b057611e0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1504,6 +1504,8 @@ static unsigned num_msrs_to_save;
 static const u32 emulated_msrs_all[] = {
 	MSR_KVM_SYSTEM_TIME, MSR_KVM_WALL_CLOCK,
 	MSR_KVM_SYSTEM_TIME_NEW, MSR_KVM_WALL_CLOCK_NEW,
+
+#ifdef CONFIG_KVM_HYPERV
 	HV_X64_MSR_GUEST_OS_ID, HV_X64_MSR_HYPERCALL,
 	HV_X64_MSR_TIME_REF_COUNT, HV_X64_MSR_REFERENCE_TSC,
 	HV_X64_MSR_TSC_FREQUENCY, HV_X64_MSR_APIC_FREQUENCY,
@@ -1521,6 +1523,7 @@ static const u32 emulated_msrs_all[] = {
 	HV_X64_MSR_SYNDBG_CONTROL, HV_X64_MSR_SYNDBG_STATUS,
 	HV_X64_MSR_SYNDBG_SEND_BUFFER, HV_X64_MSR_SYNDBG_RECV_BUFFER,
 	HV_X64_MSR_SYNDBG_PENDING_BUFFER,
+#endif
 
 	MSR_KVM_ASYNC_PF_EN, MSR_KVM_STEAL_TIME,
 	MSR_KVM_PV_EOI_EN, MSR_KVM_ASYNC_PF_INT, MSR_KVM_ASYNC_PF_ACK,
@@ -4020,6 +4023,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		 * the need to ignore the workaround.
 		 */
 		break;
+#ifdef CONFIG_KVM_HYPERV
 	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
 	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
 	case HV_X64_MSR_SYNDBG_OPTIONS:
@@ -4032,6 +4036,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 	case HV_X64_MSR_TSC_INVARIANT_CONTROL:
 		return kvm_hv_set_msr_common(vcpu, msr, data,
 					     msr_info->host_initiated);
+#endif
 	case MSR_IA32_BBL_CR_CTL3:
 		/* Drop writes to this legacy MSR -- see rdmsr
 		 * counterpart for further detail.
@@ -4377,6 +4382,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		 */
 		msr_info->data = 0x20000000;
 		break;
+#ifdef CONFIG_KVM_HYPERV
 	case HV_X64_MSR_GUEST_OS_ID ... HV_X64_MSR_SINT15:
 	case HV_X64_MSR_SYNDBG_CONTROL ... HV_X64_MSR_SYNDBG_PENDING_BUFFER:
 	case HV_X64_MSR_SYNDBG_OPTIONS:
@@ -4390,6 +4396,7 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
 		return kvm_hv_get_msr_common(vcpu,
 					     msr_info->index, &msr_info->data,
 					     msr_info->host_initiated);
+#endif
 	case MSR_IA32_BBL_CR_CTL3:
 		/* This legacy MSR exists but isn't fully documented in current
 		 * silicon.  It is however accessed by winxp in very narrow
@@ -4527,6 +4534,7 @@ static inline bool kvm_can_mwait_in_guest(void)
 		boot_cpu_has(X86_FEATURE_ARAT);
 }
 
+#ifdef CONFIG_KVM_HYPERV
 static int kvm_ioctl_get_supported_hv_cpuid(struct kvm_vcpu *vcpu,
 					    struct kvm_cpuid2 __user *cpuid_arg)
 {
@@ -4547,6 +4555,7 @@ static int kvm_ioctl_get_supported_hv_cpuid(struct kvm_vcpu *vcpu,
 
 	return 0;
 }
+#endif
 
 static bool kvm_is_vm_type_supported(unsigned long type)
 {
@@ -4580,9 +4589,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_PIT_STATE2:
 	case KVM_CAP_SET_IDENTITY_MAP_ADDR:
 	case KVM_CAP_VCPU_EVENTS:
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_CAP_HYPERV:
 	case KVM_CAP_HYPERV_VAPIC:
 	case KVM_CAP_HYPERV_SPIN:
+	case KVM_CAP_HYPERV_TIME:
 	case KVM_CAP_HYPERV_SYNIC:
 	case KVM_CAP_HYPERV_SYNIC2:
 	case KVM_CAP_HYPERV_VP_INDEX:
@@ -4592,6 +4603,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_HYPERV_CPUID:
 	case KVM_CAP_HYPERV_ENFORCE_CPUID:
 	case KVM_CAP_SYS_HYPERV_CPUID:
+#endif
 	case KVM_CAP_PCI_SEGMENT:
 	case KVM_CAP_DEBUGREGS:
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
@@ -4601,7 +4613,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_GET_TSC_KHZ:
 	case KVM_CAP_KVMCLOCK_CTRL:
 	case KVM_CAP_READONLY_MEM:
-	case KVM_CAP_HYPERV_TIME:
 	case KVM_CAP_IOAPIC_POLARITY_IGNORED:
 	case KVM_CAP_TSC_DEADLINE_TIMER:
 	case KVM_CAP_DISABLE_QUIRKS:
@@ -4712,12 +4723,14 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 		r = kvm_x86_ops.nested_ops->get_state ?
 			kvm_x86_ops.nested_ops->get_state(NULL, NULL, 0) : 0;
 		break;
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_CAP_HYPERV_DIRECT_TLBFLUSH:
 		r = kvm_x86_ops.enable_l2_tlb_flush != NULL;
 		break;
 	case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
 		r = kvm_x86_ops.nested_ops->enable_evmcs != NULL;
 		break;
+#endif
 	case KVM_CAP_SMALLER_MAXPHYADDR:
 		r = (int) allow_smaller_maxphyaddr;
 		break;
@@ -4884,9 +4897,11 @@ long kvm_arch_dev_ioctl(struct file *filp,
 	case KVM_GET_MSRS:
 		r = msr_io(NULL, argp, do_get_msr_feature, 1);
 		break;
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_GET_SUPPORTED_HV_CPUID:
 		r = kvm_ioctl_get_supported_hv_cpuid(NULL, argp);
 		break;
+#endif
 	case KVM_GET_DEVICE_ATTR: {
 		struct kvm_device_attr attr;
 		r = -EFAULT;
@@ -5712,14 +5727,11 @@ static int kvm_vcpu_ioctl_device_attr(struct kvm_vcpu *vcpu,
 static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 				     struct kvm_enable_cap *cap)
 {
-	int r;
-	uint16_t vmcs_version;
-	void __user *user_ptr;
-
 	if (cap->flags)
 		return -EINVAL;
 
 	switch (cap->cap) {
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_CAP_HYPERV_SYNIC2:
 		if (cap->args[0])
 			return -EINVAL;
@@ -5731,16 +5743,22 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 		return kvm_hv_activate_synic(vcpu, cap->cap ==
 					     KVM_CAP_HYPERV_SYNIC2);
 	case KVM_CAP_HYPERV_ENLIGHTENED_VMCS:
-		if (!kvm_x86_ops.nested_ops->enable_evmcs)
-			return -ENOTTY;
-		r = kvm_x86_ops.nested_ops->enable_evmcs(vcpu, &vmcs_version);
-		if (!r) {
-			user_ptr = (void __user *)(uintptr_t)cap->args[0];
-			if (copy_to_user(user_ptr, &vmcs_version,
-					 sizeof(vmcs_version)))
-				r = -EFAULT;
+		{
+			int r;
+			uint16_t vmcs_version;
+			void __user *user_ptr;
+
+			if (!kvm_x86_ops.nested_ops->enable_evmcs)
+				return -ENOTTY;
+			r = kvm_x86_ops.nested_ops->enable_evmcs(vcpu, &vmcs_version);
+			if (!r) {
+				user_ptr = (void __user *)(uintptr_t)cap->args[0];
+				if (copy_to_user(user_ptr, &vmcs_version,
+						 sizeof(vmcs_version)))
+					r = -EFAULT;
+			}
+			return r;
 		}
-		return r;
 	case KVM_CAP_HYPERV_DIRECT_TLBFLUSH:
 		if (!kvm_x86_ops.enable_l2_tlb_flush)
 			return -ENOTTY;
@@ -5749,6 +5767,7 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
 
 	case KVM_CAP_HYPERV_ENFORCE_CPUID:
 		return kvm_hv_set_enforce_cpuid(vcpu, cap->args[0]);
+#endif
 
 	case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
 		vcpu->arch.pv_cpuid.enforce = cap->args[0];
@@ -6141,9 +6160,11 @@ long kvm_arch_vcpu_ioctl(struct file *filp,
 		srcu_read_unlock(&vcpu->kvm->srcu, idx);
 		break;
 	}
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_GET_SUPPORTED_HV_CPUID:
 		r = kvm_ioctl_get_supported_hv_cpuid(vcpu, argp);
 		break;
+#endif
 #ifdef CONFIG_KVM_XEN
 	case KVM_XEN_VCPU_GET_ATTR: {
 		struct kvm_xen_vcpu_attr xva;
@@ -7201,6 +7222,7 @@ set_pit2_out:
 		r = static_call(kvm_x86_mem_enc_unregister_region)(kvm, &region);
 		break;
 	}
+#ifdef CONFIG_KVM_HYPERV
 	case KVM_HYPERV_EVENTFD: {
 		struct kvm_hyperv_eventfd hvevfd;
 
@@ -7210,6 +7232,7 @@ set_pit2_out:
 		r = kvm_vm_ioctl_hv_eventfd(kvm, &hvevfd);
 		break;
 	}
+#endif
 	case KVM_SET_PMU_EVENT_FILTER:
 		r = kvm_vm_ioctl_set_pmu_event_filter(kvm, argp);
 		break;
@@ -10588,19 +10611,20 @@ static void vcpu_scan_ioapic(struct kvm_vcpu *vcpu)
 
 static void vcpu_load_eoi_exitmap(struct kvm_vcpu *vcpu)
 {
-	u64 eoi_exit_bitmap[4];
-
 	if (!kvm_apic_hw_enabled(vcpu->arch.apic))
 		return;
 
+#ifdef CONFIG_KVM_HYPERV
 	if (to_hv_vcpu(vcpu)) {
+		u64 eoi_exit_bitmap[4];
+
 		bitmap_or((ulong *)eoi_exit_bitmap,
 			  vcpu->arch.ioapic_handled_vectors,
 			  to_hv_synic(vcpu)->vec_bitmap, 256);
 		static_call_cond(kvm_x86_load_eoi_exitmap)(vcpu, eoi_exit_bitmap);
 		return;
 	}
-
+#endif
 	static_call_cond(kvm_x86_load_eoi_exitmap)(
 		vcpu, (u64 *)vcpu->arch.ioapic_handled_vectors);
 }
@@ -10691,9 +10715,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		 * the flushes are considered "remote" and not "local" because
 		 * the requests can be initiated from other vCPUs.
 		 */
+#ifdef CONFIG_KVM_HYPERV
 		if (kvm_check_request(KVM_REQ_HV_TLB_FLUSH, vcpu) &&
 		    kvm_hv_vcpu_flush_tlb(vcpu))
 			kvm_vcpu_flush_tlb_guest(vcpu);
+#endif
 
 		if (kvm_check_request(KVM_REQ_REPORT_TPR_ACCESS, vcpu)) {
 			vcpu->run->exit_reason = KVM_EXIT_TPR_ACCESS;
@@ -10746,6 +10772,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 			vcpu_load_eoi_exitmap(vcpu);
 		if (kvm_check_request(KVM_REQ_APIC_PAGE_RELOAD, vcpu))
 			kvm_vcpu_reload_apic_access_page(vcpu);
+#ifdef CONFIG_KVM_HYPERV
 		if (kvm_check_request(KVM_REQ_HV_CRASH, vcpu)) {
 			vcpu->run->exit_reason = KVM_EXIT_SYSTEM_EVENT;
 			vcpu->run->system_event.type = KVM_SYSTEM_EVENT_CRASH;
@@ -10776,6 +10803,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		 */
 		if (kvm_check_request(KVM_REQ_HV_STIMER, vcpu))
 			kvm_hv_process_stimers(vcpu);
+#endif
 		if (kvm_check_request(KVM_REQ_APICV_UPDATE, vcpu))
 			kvm_vcpu_update_apicv(vcpu);
 		if (kvm_check_request(KVM_REQ_APF_READY, vcpu))