KVM: x86/mmu: Separate the memory caches for shadow pages and gfn arrays

Use separate caches for allocating shadow pages versus gfn arrays.  This
sets the stage for specifying __GFP_ZERO when allocating shadow pages
without incurring extra cost for gfn arrays.

No functional change intended.
Reviewed-by: Ben Gardon <bgardon@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200703023545.8771-10-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_host.h

@@ -602,7 +602,8 @@ struct kvm_vcpu_arch {
 	struct kvm_mmu *walk_mmu;
 
 	struct kvm_mmu_memory_cache mmu_pte_list_desc_cache;
-	struct kvm_mmu_memory_cache mmu_page_cache;
+	struct kvm_mmu_memory_cache mmu_shadow_page_cache;
+	struct kvm_mmu_memory_cache mmu_gfn_array_cache;
 	struct kvm_mmu_memory_cache mmu_page_header_cache;
 
 	/*

arch/x86/kvm/mmu/mmu.c

@@ -1109,8 +1109,12 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 				   1 + PT64_ROOT_MAX_LEVEL + PTE_PREFETCH_NUM);
 	if (r)
 		return r;
-	r = mmu_topup_memory_cache(&vcpu->arch.mmu_page_cache,
-				   2 * PT64_ROOT_MAX_LEVEL);
+	r = mmu_topup_memory_cache(&vcpu->arch.mmu_shadow_page_cache,
+				   PT64_ROOT_MAX_LEVEL);
+	if (r)
+		return r;
+	r = mmu_topup_memory_cache(&vcpu->arch.mmu_gfn_array_cache,
+				   PT64_ROOT_MAX_LEVEL);
 	if (r)
 		return r;
 	return mmu_topup_memory_cache(&vcpu->arch.mmu_page_header_cache,
@@ -1120,7 +1124,8 @@ static int mmu_topup_memory_caches(struct kvm_vcpu *vcpu)
 static void mmu_free_memory_caches(struct kvm_vcpu *vcpu)
 {
 	mmu_free_memory_cache(&vcpu->arch.mmu_pte_list_desc_cache);
-	mmu_free_memory_cache(&vcpu->arch.mmu_page_cache);
+	mmu_free_memory_cache(&vcpu->arch.mmu_shadow_page_cache);
+	mmu_free_memory_cache(&vcpu->arch.mmu_gfn_array_cache);
 	mmu_free_memory_cache(&vcpu->arch.mmu_page_header_cache);
 }
 
@@ -2082,9 +2087,9 @@ static struct kvm_mmu_page *kvm_mmu_alloc_page(struct kvm_vcpu *vcpu, int direct
 	struct kvm_mmu_page *sp;
 
 	sp = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_header_cache);
-	sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
+	sp->spt = mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
 	if (!direct)
-		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_page_cache);
+		sp->gfns = mmu_memory_cache_alloc(&vcpu->arch.mmu_gfn_array_cache);
 	set_page_private(virt_to_page(sp->spt), (unsigned long)sp);
 
 	/*