KVM: VMX: Stuff vcpu->arch.apic_base directly at vCPU RESET

Write vcpu->arch.apic_base directly instead of bouncing through
kvm_set_apic_base().  This is a glorified nop, and is a step towards
cleaning up the mess that is local APIC creation.

When using an in-kernel APIC, kvm_create_lapic() explicitly sets
vcpu->arch.apic_base to MSR_IA32_APICBASE_ENABLE to avoid its own
kvm_lapic_set_base() call in kvm_lapic_reset() from triggering state
changes.  That call during RESET exists purely to set apic->base_address
to the default base value.  As a result, by the time VMX gets control,
the only missing piece is the BSP bit being set for the reset BSP.

For a userspace APIC, there are no side effects to process (for the APIC).

In both cases, the call to kvm_update_cpuid_runtime() is a nop because
the vCPU hasn't yet been exposed to userspace, i.e. there can't be any
CPUID entries.

No functional change intended.
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210713163324.627647-17-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/vmx/vmx.c

@@ -4391,7 +4391,6 @@ static void init_vmcs(struct vcpu_vmx *vmx)
 static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
-	struct msr_data apic_base_msr;
 	u32 eax, dummy;
 	u64 cr0;
 
@@ -4409,12 +4408,10 @@ static void vmx_vcpu_reset(struct kvm_vcpu *vcpu, bool init_event)
 	kvm_set_cr8(vcpu, 0);
 
 	if (!init_event) {
-		apic_base_msr.data = APIC_DEFAULT_PHYS_BASE |
-				     MSR_IA32_APICBASE_ENABLE;
+		vcpu->arch.apic_base = APIC_DEFAULT_PHYS_BASE |
+				       MSR_IA32_APICBASE_ENABLE;
 		if (kvm_vcpu_is_reset_bsp(vcpu))
-			apic_base_msr.data |= MSR_IA32_APICBASE_BSP;
-		apic_base_msr.host_initiated = true;
-		kvm_set_apic_base(vcpu, &apic_base_msr);
+			vcpu->arch.apic_base |= MSR_IA32_APICBASE_BSP;
 	}
 
 	vmx_segment_cache_clear(vmx);