KVM: arm64: Combine visitor arguments into a context structure

Passing new arguments by value to the visitor callbacks is extremely
inflexible for stuffing new parameters used by only some of the
visitors. Use a context structure instead and pass the pointer through
to the visitor callback.

While at it, redefine the 'flags' parameter to the visitor to contain
the bit indicating the phase of the walk. Pass the entire set of flags
through the context structure such that the walker can communicate
additional state to the visitor callback.

No functional change intended.
Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Reviewed-by: Ben Gardon <bgardon@google.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221107215644.1895162-2-oliver.upton@linux.dev

arch/arm64/include/asm/kvm_pgtable.h

@@ -199,10 +199,17 @@ enum kvm_pgtable_walk_flags {
 	KVM_PGTABLE_WALK_TABLE_POST		= BIT(2),
 };
 
-typedef int (*kvm_pgtable_visitor_fn_t)(u64 addr, u64 end, u32 level,
-					kvm_pte_t *ptep,
-					enum kvm_pgtable_walk_flags flag,
-					void * const arg);
+struct kvm_pgtable_visit_ctx {
+	kvm_pte_t				*ptep;
+	void					*arg;
+	u64					addr;
+	u64					end;
+	u32					level;
+	enum kvm_pgtable_walk_flags		flags;
+};
+
+typedef int (*kvm_pgtable_visitor_fn_t)(const struct kvm_pgtable_visit_ctx *ctx,
+					enum kvm_pgtable_walk_flags visit);
 
 /**
  * struct kvm_pgtable_walker - Hook into a page-table walk.

arch/arm64/kvm/hyp/nvhe/mem_protect.c

@@ -417,13 +417,11 @@ struct check_walk_data {
 	enum pkvm_page_state	(*get_page_state)(kvm_pte_t pte);
 };
 
-static int __check_page_state_visitor(u64 addr, u64 end, u32 level,
-				      kvm_pte_t *ptep,
-				      enum kvm_pgtable_walk_flags flag,
-				      void * const arg)
+static int __check_page_state_visitor(const struct kvm_pgtable_visit_ctx *ctx,
+				      enum kvm_pgtable_walk_flags visit)
 {
-	struct check_walk_data *d = arg;
-	kvm_pte_t pte = *ptep;
+	struct check_walk_data *d = ctx->arg;
+	kvm_pte_t pte = *ctx->ptep;
 
 	if (kvm_pte_valid(pte) && !addr_is_memory(kvm_pte_to_phys(pte)))
 		return -EINVAL;

arch/arm64/kvm/hyp/nvhe/setup.c

@@ -186,15 +186,13 @@ static void hpool_put_page(void *addr)
 	hyp_put_page(&hpool, addr);
 }
 
-static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level,
-					 kvm_pte_t *ptep,
-					 enum kvm_pgtable_walk_flags flag,
-					 void * const arg)
+static int finalize_host_mappings_walker(const struct kvm_pgtable_visit_ctx *ctx,
+					 enum kvm_pgtable_walk_flags visit)
 {
-	struct kvm_pgtable_mm_ops *mm_ops = arg;
+	struct kvm_pgtable_mm_ops *mm_ops = ctx->arg;
 	enum kvm_pgtable_prot prot;
 	enum pkvm_page_state state;
-	kvm_pte_t pte = *ptep;
+	kvm_pte_t pte = *ctx->ptep;
 	phys_addr_t phys;
 
 	if (!kvm_pte_valid(pte))
@@ -205,11 +203,11 @@ static int finalize_host_mappings_walker(u64 addr, u64 end, u32 level,
 	 * was unable to access the hyp_vmemmap and so the buddy allocator has
 	 * initialised the refcount to '1'.
 	 */
-	mm_ops->get_page(ptep);
-	if (flag != KVM_PGTABLE_WALK_LEAF)
+	mm_ops->get_page(ctx->ptep);
+	if (visit != KVM_PGTABLE_WALK_LEAF)
 		return 0;
 
-	if (level != (KVM_PGTABLE_MAX_LEVELS - 1))
+	if (ctx->level != (KVM_PGTABLE_MAX_LEVELS - 1))
 		return -EINVAL;
 
 	phys = kvm_pte_to_phys(pte);