KVM: x86/mmu: Move TDP MMU VM init/uninit behind tdp_mmu_enabled

Move kvm_mmu_{init,uninit}_tdp_mmu() behind tdp_mmu_enabled. This makes
these functions consistent with the rest of the calls into the TDP MMU
from mmu.c, and which is now possible since tdp_mmu_enabled is only
modified when the x86 vendor module is loaded. i.e. It will never change
during the lifetime of a VM.

This change also enabled removing the stub definitions for 32-bit KVM,
as the compiler will just optimize the calls out like it does for all
the other TDP MMU functions.

No functional change intended.
Signed-off-by: David Matlack <dmatlack@google.com>
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220921173546.2674386-3-dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/mmu/mmu.c

@@ -6035,9 +6035,11 @@ int kvm_mmu_init_vm(struct kvm *kvm)
 	INIT_LIST_HEAD(&kvm->arch.possible_nx_huge_pages);
 	spin_lock_init(&kvm->arch.mmu_unsync_pages_lock);
 
-	r = kvm_mmu_init_tdp_mmu(kvm);
-	if (r < 0)
-		return r;
+	if (tdp_mmu_enabled) {
+		r = kvm_mmu_init_tdp_mmu(kvm);
+		if (r < 0)
+			return r;
+	}
 
 	node->track_write = kvm_mmu_pte_write;
 	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
@@ -6067,7 +6069,8 @@ void kvm_mmu_uninit_vm(struct kvm *kvm)
 
 	kvm_page_track_unregister_notifier(kvm, node);
 
-	kvm_mmu_uninit_tdp_mmu(kvm);
+	if (tdp_mmu_enabled)
+		kvm_mmu_uninit_tdp_mmu(kvm);
 
 	mmu_free_vm_memory_caches(kvm);
 }

arch/x86/kvm/mmu/tdp_mmu.c

@@ -15,9 +15,6 @@ int kvm_mmu_init_tdp_mmu(struct kvm *kvm)
 {
 	struct workqueue_struct *wq;
 
-	if (!tdp_mmu_enabled)
-		return 0;
-
 	wq = alloc_workqueue("kvm", WQ_UNBOUND|WQ_MEM_RECLAIM|WQ_CPU_INTENSIVE, 0);
 	if (!wq)
 		return -ENOMEM;
@@ -42,9 +39,6 @@ static __always_inline bool kvm_lockdep_assert_mmu_lock_held(struct kvm *kvm,
 
 void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm)
 {
-	if (!tdp_mmu_enabled)
-		return;
-
 	/* Also waits for any queued work items.  */
 	destroy_workqueue(kvm->arch.tdp_mmu_zap_wq);
 

arch/x86/kvm/mmu/tdp_mmu.h

@@ -7,6 +7,9 @@
 
 #include "spte.h"
 
+int kvm_mmu_init_tdp_mmu(struct kvm *kvm);
+void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm);
+
 hpa_t kvm_tdp_mmu_get_vcpu_root_hpa(struct kvm_vcpu *vcpu);
 
 __must_check static inline bool kvm_tdp_mmu_get_root(struct kvm_mmu_page *root)
@@ -68,8 +71,6 @@ u64 *kvm_tdp_mmu_fast_pf_get_last_sptep(struct kvm_vcpu *vcpu, u64 addr,
 					u64 *spte);
 
 #ifdef CONFIG_X86_64
-int kvm_mmu_init_tdp_mmu(struct kvm *kvm);
-void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm);
 static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return sp->tdp_mmu_page; }
 
 static inline bool is_tdp_mmu(struct kvm_mmu *mmu)
@@ -89,8 +90,6 @@ static inline bool is_tdp_mmu(struct kvm_mmu *mmu)
 	return sp && is_tdp_mmu_page(sp) && sp->root_count;
 }
 #else
-static inline int kvm_mmu_init_tdp_mmu(struct kvm *kvm) { return 0; }
-static inline void kvm_mmu_uninit_tdp_mmu(struct kvm *kvm) {}
 static inline bool is_tdp_mmu_page(struct kvm_mmu_page *sp) { return false; }
 static inline bool is_tdp_mmu(struct kvm_mmu *mmu) { return false; }
 #endif