KVM: X86: Reduce size of kvm_vcpu_arch structure when CONFIG_KVM_XEN=n

When CONFIG_KVM_XEN=n, the size of kvm_vcpu_arch can be reduced
from 5100+ to 4400+ by adding macro control.
Signed-off-by: Peng Hao <flyingpeng@tencent.com>
Link: https://lore.kernel.org/all/CAPm50aKwbZGeXPK5uig18Br8CF1hOS71CE2j_dLX+ub7oJdpGg@mail.gmail.com
[sean: fix whitespace damage]
Signed-off-by: Sean Christopherson <seanjc@google.com>

arch/x86/include/asm/kvm_host.h

@@ -680,6 +680,7 @@ struct kvm_hypervisor_cpuid {
 	u32 limit;
 };
 
+#ifdef CONFIG_KVM_XEN
 /* Xen HVM per vcpu emulation context */
 struct kvm_vcpu_xen {
 	u64 hypercall_rip;
@@ -702,6 +703,7 @@ struct kvm_vcpu_xen {
 	struct timer_list poll_timer;
 	struct kvm_hypervisor_cpuid cpuid;
 };
+#endif
 
 struct kvm_queued_exception {
 	bool pending;
@@ -930,8 +932,9 @@ struct kvm_vcpu_arch {
 
 	bool hyperv_enabled;
 	struct kvm_vcpu_hv *hyperv;
+#ifdef CONFIG_KVM_XEN
 	struct kvm_vcpu_xen xen;
-
+#endif
 	cpumask_var_t wbinvd_dirty_mask;
 
 	unsigned long last_retry_eip;

arch/x86/kvm/cpuid.c

@@ -456,7 +456,9 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
 	vcpu->arch.cpuid_nent = nent;
 
 	vcpu->arch.kvm_cpuid = kvm_get_hypervisor_cpuid(vcpu, KVM_SIGNATURE);
+#ifdef CONFIG_KVM_XEN
 	vcpu->arch.xen.cpuid = kvm_get_hypervisor_cpuid(vcpu, XEN_SIGNATURE);
+#endif
 	kvm_vcpu_after_set_cpuid(vcpu);
 
 	return 0;

arch/x86/kvm/x86.c

@@ -3232,11 +3232,13 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
 
 	if (vcpu->pv_time.active)
 		kvm_setup_guest_pvclock(v, &vcpu->pv_time, 0);
+#ifdef CONFIG_KVM_XEN
 	if (vcpu->xen.vcpu_info_cache.active)
 		kvm_setup_guest_pvclock(v, &vcpu->xen.vcpu_info_cache,
 					offsetof(struct compat_vcpu_info, time));
 	if (vcpu->xen.vcpu_time_info_cache.active)
 		kvm_setup_guest_pvclock(v, &vcpu->xen.vcpu_time_info_cache, 0);
+#endif
 	kvm_hv_setup_tsc_page(v->kvm, &vcpu->hv_clock);
 	return 0;
 }