KVM: arm64: Factor memory allocation out of pgtable.c

In preparation for enabling the creation of page-tables at EL2, factor
all memory allocation out of the page-table code, hence making it
re-usable with any compatible memory allocator.

No functional changes intended.
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-7-qperret@google.com

arch/arm64/include/asm/kvm_pgtable.h

@@ -13,17 +13,50 @@
 
 typedef u64 kvm_pte_t;
 
+/**
+ * struct kvm_pgtable_mm_ops - Memory management callbacks.
+ * @zalloc_page:	Allocate a single zeroed memory page. The @arg parameter
+ *			can be used by the walker to pass a memcache. The
+ *			initial refcount of the page is 1.
+ * @zalloc_pages_exact:	Allocate an exact number of zeroed memory pages. The
+ *			@size parameter is in bytes, and is rounded-up to the
+ *			next page boundary. The resulting allocation is
+ *			physically contiguous.
+ * @free_pages_exact:	Free an exact number of memory pages previously
+ *			allocated by zalloc_pages_exact.
+ * @get_page:		Increment the refcount on a page.
+ * @put_page:		Decrement the refcount on a page. When the refcount
+ *			reaches 0 the page is automatically freed.
+ * @page_count:		Return the refcount of a page.
+ * @phys_to_virt:	Convert a physical address into a virtual address mapped
+ *			in the current context.
+ * @virt_to_phys:	Convert a virtual address mapped in the current context
+ *			into a physical address.
+ */
+struct kvm_pgtable_mm_ops {
+	void*		(*zalloc_page)(void *arg);
+	void*		(*zalloc_pages_exact)(size_t size);
+	void		(*free_pages_exact)(void *addr, size_t size);
+	void		(*get_page)(void *addr);
+	void		(*put_page)(void *addr);
+	int		(*page_count)(void *addr);
+	void*		(*phys_to_virt)(phys_addr_t phys);
+	phys_addr_t	(*virt_to_phys)(void *addr);
+};
+
 /**
  * struct kvm_pgtable - KVM page-table.
  * @ia_bits:		Maximum input address size, in bits.
  * @start_level:	Level at which the page-table walk starts.
  * @pgd:		Pointer to the first top-level entry of the page-table.
+ * @mm_ops:		Memory management callbacks.
  * @mmu:		Stage-2 KVM MMU struct. Unused for stage-1 page-tables.
  */
 struct kvm_pgtable {
 	u32					ia_bits;
 	u32					start_level;
 	kvm_pte_t				*pgd;
+	struct kvm_pgtable_mm_ops		*mm_ops;
 
 	/* Stage-2 only */
 	struct kvm_s2_mmu			*mmu;
@@ -86,10 +119,12 @@ struct kvm_pgtable_walker {
  * kvm_pgtable_hyp_init() - Initialise a hypervisor stage-1 page-table.
  * @pgt:	Uninitialised page-table structure to initialise.
  * @va_bits:	Maximum virtual address bits.
+ * @mm_ops:	Memory management callbacks.
  *
  * Return: 0 on success, negative error code on failure.
  */
-int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits);
+int kvm_pgtable_hyp_init(struct kvm_pgtable *pgt, u32 va_bits,
+			 struct kvm_pgtable_mm_ops *mm_ops);
 
 /**
  * kvm_pgtable_hyp_destroy() - Destroy an unused hypervisor stage-1 page-table.
@@ -126,10 +161,12 @@ int kvm_pgtable_hyp_map(struct kvm_pgtable *pgt, u64 addr, u64 size, u64 phys,
  * kvm_pgtable_stage2_init() - Initialise a guest stage-2 page-table.
  * @pgt:	Uninitialised page-table structure to initialise.
  * @kvm:	KVM structure representing the guest virtual machine.
+ * @mm_ops:	Memory management callbacks.
  *
  * Return: 0 on success, negative error code on failure.
  */
-int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm);
+int kvm_pgtable_stage2_init(struct kvm_pgtable *pgt, struct kvm *kvm,
+			    struct kvm_pgtable_mm_ops *mm_ops);
 
 /**
  * kvm_pgtable_stage2_destroy() - Destroy an unused guest stage-2 page-table.

arch/arm64/kvm/mmu.c

@@ -88,6 +88,44 @@ static bool kvm_is_device_pfn(unsigned long pfn)
 	return !pfn_valid(pfn);
 }
 
+static void *stage2_memcache_zalloc_page(void *arg)
+{
+	struct kvm_mmu_memory_cache *mc = arg;
+
+	/* Allocated with __GFP_ZERO, so no need to zero */
+	return kvm_mmu_memory_cache_alloc(mc);
+}
+
+static void *kvm_host_zalloc_pages_exact(size_t size)
+{
+	return alloc_pages_exact(size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
+}
+
+static void kvm_host_get_page(void *addr)
+{
+	get_page(virt_to_page(addr));
+}
+
+static void kvm_host_put_page(void *addr)
+{
+	put_page(virt_to_page(addr));
+}
+
+static int kvm_host_page_count(void *addr)
+{
+	return page_count(virt_to_page(addr));
+}
+
+static phys_addr_t kvm_host_pa(void *addr)
+{
+	return __pa(addr);
+}
+
+static void *kvm_host_va(phys_addr_t phys)
+{
+	return __va(phys);
+}
+
 /*
  * Unmapping vs dcache management:
  *
@@ -351,6 +389,17 @@ int create_hyp_exec_mappings(phys_addr_t phys_addr, size_t size,
 	return 0;
 }
 
+static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
+	.zalloc_page		= stage2_memcache_zalloc_page,
+	.zalloc_pages_exact	= kvm_host_zalloc_pages_exact,
+	.free_pages_exact	= free_pages_exact,
+	.get_page		= kvm_host_get_page,
+	.put_page		= kvm_host_put_page,
+	.page_count		= kvm_host_page_count,
+	.phys_to_virt		= kvm_host_va,
+	.virt_to_phys		= kvm_host_pa,
+};
+
 /**
  * kvm_init_stage2_mmu - Initialise a S2 MMU strucrure
  * @kvm:	The pointer to the KVM structure
@@ -374,7 +423,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu)
 	if (!pgt)
 		return -ENOMEM;
 
-	err = kvm_pgtable_stage2_init(pgt, kvm);
+	err = kvm_pgtable_stage2_init(pgt, kvm, &kvm_s2_mm_ops);
 	if (err)
 		goto out_free_pgtable;
 
@@ -1208,6 +1257,19 @@ static int kvm_map_idmap_text(void)
 	return err;
 }
 
+static void *kvm_hyp_zalloc_page(void *arg)
+{
+	return (void *)get_zeroed_page(GFP_KERNEL);
+}
+
+static struct kvm_pgtable_mm_ops kvm_hyp_mm_ops = {
+	.zalloc_page		= kvm_hyp_zalloc_page,
+	.get_page		= kvm_host_get_page,
+	.put_page		= kvm_host_put_page,
+	.phys_to_virt		= kvm_host_va,
+	.virt_to_phys		= kvm_host_pa,
+};
+
 int kvm_mmu_init(void)
 {
 	int err;
@@ -1251,7 +1313,7 @@ int kvm_mmu_init(void)
 		goto out;
 	}
 
-	err = kvm_pgtable_hyp_init(hyp_pgtable, hyp_va_bits);
+	err = kvm_pgtable_hyp_init(hyp_pgtable, hyp_va_bits, &kvm_hyp_mm_ops);
 	if (err)
 		goto out_free_pgtable;