KVM: VMX: Add a macro to track which DEBUGCTL bits are host-owned

Add VMX_HOST_OWNED_DEBUGCTL_BITS to track which bits are host-owned, i.e.
need to be preserved when running the guest, to dedup the logic without
having to incur a memory load to get at kvm_x86_ops.HOST_OWNED_DEBUGCTL.

No functional change intended.

Suggested-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Link: https://lore.kernel.org/all/aF1yni8U6XNkyfRf@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/x86/kvm/vmx/main.c

@@ -915,7 +915,7 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
 	.vcpu_load = vt_op(vcpu_load),
 	.vcpu_put = vt_op(vcpu_put),
 
-	.HOST_OWNED_DEBUGCTL = DEBUGCTLMSR_FREEZE_IN_SMM,
+	.HOST_OWNED_DEBUGCTL = VMX_HOST_OWNED_DEBUGCTL_BITS,
 
 	.update_exception_bitmap = vt_op(update_exception_bitmap),
 	.get_feature_msr = vmx_get_feature_msr,

arch/x86/kvm/vmx/vmx.h

@@ -410,27 +410,29 @@ void vmx_update_cpu_dirty_logging(struct kvm_vcpu *vcpu);
 u64 vmx_get_supported_debugctl(struct kvm_vcpu *vcpu, bool host_initiated);
 bool vmx_is_valid_debugctl(struct kvm_vcpu *vcpu, u64 data, bool host_initiated);
 
+#define VMX_HOST_OWNED_DEBUGCTL_BITS	(DEBUGCTLMSR_FREEZE_IN_SMM)
+
 static inline void vmx_guest_debugctl_write(struct kvm_vcpu *vcpu, u64 val)
 {
-	WARN_ON_ONCE(val & DEBUGCTLMSR_FREEZE_IN_SMM);
+	WARN_ON_ONCE(val & VMX_HOST_OWNED_DEBUGCTL_BITS);
 
-	val |= vcpu->arch.host_debugctl & DEBUGCTLMSR_FREEZE_IN_SMM;
+	val |= vcpu->arch.host_debugctl & VMX_HOST_OWNED_DEBUGCTL_BITS;
 	vmcs_write64(GUEST_IA32_DEBUGCTL, val);
 }
 
 static inline u64 vmx_guest_debugctl_read(void)
 {
-	return vmcs_read64(GUEST_IA32_DEBUGCTL) & ~DEBUGCTLMSR_FREEZE_IN_SMM;
+	return vmcs_read64(GUEST_IA32_DEBUGCTL) & ~VMX_HOST_OWNED_DEBUGCTL_BITS;
 }
 
 static inline void vmx_reload_guest_debugctl(struct kvm_vcpu *vcpu)
 {
 	u64 val = vmcs_read64(GUEST_IA32_DEBUGCTL);
 
-	if (!((val ^ vcpu->arch.host_debugctl) & DEBUGCTLMSR_FREEZE_IN_SMM))
+	if (!((val ^ vcpu->arch.host_debugctl) & VMX_HOST_OWNED_DEBUGCTL_BITS))
 		return;
 
-	vmx_guest_debugctl_write(vcpu, val & ~DEBUGCTLMSR_FREEZE_IN_SMM);
+	vmx_guest_debugctl_write(vcpu, val & ~VMX_HOST_OWNED_DEBUGCTL_BITS);
 }
 
 /*