KVM: arm64: pkvm: Fix hyp_pool max order

The EL2 page allocator in protected mode maintains a per-pool max order
value to optimize allocations when the memory region it covers is small.
However, the max order value is currently under-estimated whenever the
number of pages in the region is a power of two. Fix the estimation.
Signed-off-by: Quentin Perret <qperret@google.com>
Acked-by: Will Deacon <will@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20211208152300.2478542-2-qperret@google.com

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

@@ -241,7 +241,7 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
 	int i;
 
 	hyp_spin_lock_init(&pool->lock);
-	pool->max_order = min(MAX_ORDER, get_order(nr_pages << PAGE_SHIFT));
+	pool->max_order = min(MAX_ORDER, get_order((nr_pages + 1) << PAGE_SHIFT));
 	for (i = 0; i < pool->max_order; i++)
 		INIT_LIST_HEAD(&pool->free_area[i]);
 	pool->range_start = phys;