KVM: arm64: Use less bits for hyp_page order

The hyp_page order is currently encoded on 4 bytes even though it is
guaranteed to be smaller than this. Make it 2 bytes to reduce the hyp
vmemmap overhead.

Signed-off-by: Quentin Perret <qperret@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210608114518.748712-7-qperret@google.com

Author: Quentin Perret

arch/arm64/kvm/hyp/include/nvhe/gfp.h

@@ -7,7 +7,7 @@
 #include <nvhe/memory.h>
 #include <nvhe/spinlock.h>
 
-#define HYP_NO_ORDER	UINT_MAX
+#define HYP_NO_ORDER	USHRT_MAX
 
 struct hyp_pool {
 	/*
@@ -19,11 +19,11 @@ struct hyp_pool {
 	struct list_head free_area[MAX_ORDER];
 	phys_addr_t range_start;
 	phys_addr_t range_end;
-	unsigned int max_order;
+	unsigned short max_order;
 };
 
 /* Allocation */
-void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order);
+void *hyp_alloc_pages(struct hyp_pool *pool, unsigned short order);
 void hyp_get_page(struct hyp_pool *pool, void *addr);
 void hyp_put_page(struct hyp_pool *pool, void *addr);
 

arch/arm64/kvm/hyp/include/nvhe/memory.h

@@ -9,7 +9,7 @@
 
 struct hyp_page {
 	unsigned int refcount;
-	unsigned int order;
+	unsigned short order;
 };
 
 extern u64 __hyp_vmemmap;

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

@@ -32,7 +32,7 @@ u64 __hyp_vmemmap;
  */
 static struct hyp_page *__find_buddy_nocheck(struct hyp_pool *pool,
 					     struct hyp_page *p,
-					     unsigned int order)
+					     unsigned short order)
 {
 	phys_addr_t addr = hyp_page_to_phys(p);
 
@@ -51,7 +51,7 @@ static struct hyp_page *__find_buddy_nocheck(struct hyp_pool *pool,
 /* Find a buddy page currently available for allocation */
 static struct hyp_page *__find_buddy_avail(struct hyp_pool *pool,
 					   struct hyp_page *p,
-					   unsigned int order)
+					   unsigned short order)
 {
 	struct hyp_page *buddy = __find_buddy_nocheck(pool, p, order);
 
@@ -93,7 +93,7 @@ static inline struct hyp_page *node_to_page(struct list_head *node)
 static void __hyp_attach_page(struct hyp_pool *pool,
 			      struct hyp_page *p)
 {
-	unsigned int order = p->order;
+	unsigned short order = p->order;
 	struct hyp_page *buddy;
 
 	memset(hyp_page_to_virt(p), 0, PAGE_SIZE << p->order);
@@ -123,7 +123,7 @@ static void __hyp_attach_page(struct hyp_pool *pool,
 
 static struct hyp_page *__hyp_extract_page(struct hyp_pool *pool,
 					   struct hyp_page *p,
-					   unsigned int order)
+					   unsigned short order)
 {
 	struct hyp_page *buddy;
 
@@ -192,9 +192,9 @@ void hyp_get_page(struct hyp_pool *pool, void *addr)
 	hyp_spin_unlock(&pool->lock);
 }
 
-void *hyp_alloc_pages(struct hyp_pool *pool, unsigned int order)
+void *hyp_alloc_pages(struct hyp_pool *pool, unsigned short order)
 {
-	unsigned int i = order;
+	unsigned short i = order;
 	struct hyp_page *p;
 
 	hyp_spin_lock(&pool->lock);