powerpc/kvm: Switch kvm pmd allocator to custom allocator

In the next set of patches, we will switch pmd allocator to use page fragments
and the locking will be updated to split pmd ptlock. We want to avoid using
fragments for partition-scoped table. Use slab cache similar to level 4 table

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kvm/book3s_64_mmu_radix.c

@@ -200,6 +200,7 @@ void kvmppc_radix_set_pte_at(struct kvm *kvm, unsigned long addr,
 }
 
 static struct kmem_cache *kvm_pte_cache;
+static struct kmem_cache *kvm_pmd_cache;
 
 static pte_t *kvmppc_pte_alloc(void)
 {
@@ -217,6 +218,16 @@ static inline int pmd_is_leaf(pmd_t pmd)
 	return !!(pmd_val(pmd) & _PAGE_PTE);
 }
 
+static pmd_t *kvmppc_pmd_alloc(void)
+{
+	return kmem_cache_alloc(kvm_pmd_cache, GFP_KERNEL);
+}
+
+static void kvmppc_pmd_free(pmd_t *pmdp)
+{
+	kmem_cache_free(kvm_pmd_cache, pmdp);
+}
+
 static int kvmppc_create_pte(struct kvm *kvm, pte_t pte, unsigned long gpa,
 			     unsigned int level, unsigned long mmu_seq)
 {
@@ -239,7 +250,7 @@ static int kvmppc_create_pte(struct kvm *kvm, pte_t pte, unsigned long gpa,
 	if (pud && pud_present(*pud) && !pud_huge(*pud))
 		pmd = pmd_offset(pud, gpa);
 	else if (level <= 1)
-		new_pmd = pmd_alloc_one(kvm->mm, gpa);
+		new_pmd = kvmppc_pmd_alloc();
 
 	if (level == 0 && !(pmd && pmd_present(*pmd) && !pmd_is_leaf(*pmd)))
 		new_ptep = kvmppc_pte_alloc();
@@ -382,7 +393,7 @@ static int kvmppc_create_pte(struct kvm *kvm, pte_t pte, unsigned long gpa,
 	if (new_pud)
 		pud_free(kvm->mm, new_pud);
 	if (new_pmd)
-		pmd_free(kvm->mm, new_pmd);
+		kvmppc_pmd_free(new_pmd);
 	if (new_ptep)
 		kvmppc_pte_free(new_ptep);
 	return ret;
@@ -758,7 +769,7 @@ void kvmppc_free_radix(struct kvm *kvm)
 				kvmppc_pte_free(pte);
 				pmd_clear(pmd);
 			}
-			pmd_free(kvm->mm, pmd_offset(pud, 0));
+			kvmppc_pmd_free(pmd_offset(pud, 0));
 			pud_clear(pud);
 		}
 		pud_free(kvm->mm, pud_offset(pgd, 0));
@@ -770,20 +781,35 @@ void kvmppc_free_radix(struct kvm *kvm)
 
 static void pte_ctor(void *addr)
 {
-	memset(addr, 0, PTE_TABLE_SIZE);
+	memset(addr, 0, RADIX_PTE_TABLE_SIZE);
+}
+
+static void pmd_ctor(void *addr)
+{
+	memset(addr, 0, RADIX_PMD_TABLE_SIZE);
 }
 
 int kvmppc_radix_init(void)
 {
-	unsigned long size = sizeof(void *) << PTE_INDEX_SIZE;
+	unsigned long size = sizeof(void *) << RADIX_PTE_INDEX_SIZE;
 
 	kvm_pte_cache = kmem_cache_create("kvm-pte", size, size, 0, pte_ctor);
 	if (!kvm_pte_cache)
 		return -ENOMEM;
+
+	size = sizeof(void *) << RADIX_PMD_INDEX_SIZE;
+
+	kvm_pmd_cache = kmem_cache_create("kvm-pmd", size, size, 0, pmd_ctor);
+	if (!kvm_pmd_cache) {
+		kmem_cache_destroy(kvm_pte_cache);
+		return -ENOMEM;
+	}
+
 	return 0;
 }
 
 void kvmppc_radix_exit(void)
 {
 	kmem_cache_destroy(kvm_pte_cache);
+	kmem_cache_destroy(kvm_pmd_cache);
 }