powerpc/iommu: Allocate it_map by vmalloc

The IOMMU table uses the it_map bitmap to keep track of allocated DMA
pages. This has always been a contiguous array allocated at either
the boot time or when a passed through device is returned to the host OS.
The it_map memory is allocated by alloc_pages() which allocates
contiguous physical memory.

Such allocation method occasionally creates a problem when there is
no big chunk of memory available (no free memory or too fragmented).
On powernv/ioda2 the default DMA window requires 16MB for it_map.

This replaces alloc_pages_node() with vzalloc_node() which allocates
contiguous block but in virtual memory. This should reduce changes of
failure but should not cause other behavioral changes as it_map is only
used by the kernel's DMA hooks/api when MMU is on.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210216033307.69863-2-aik@ozlabs.ru

arch/powerpc/kernel/iommu.c

@@ -718,7 +718,6 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid,
 {
 	unsigned long sz;
 	static int welcomed = 0;
-	struct page *page;
 	unsigned int i;
 	struct iommu_pool *p;
 
@@ -727,11 +726,9 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid,
 	/* number of bytes needed for the bitmap */
 	sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
 
-	page = alloc_pages_node(nid, GFP_KERNEL, get_order(sz));
-	if (!page)
+	tbl->it_map = vzalloc_node(sz, nid);
+	if (!tbl->it_map)
 		panic("iommu_init_table: Can't allocate %ld bytes\n", sz);
-	tbl->it_map = page_address(page);
-	memset(tbl->it_map, 0, sz);
 
 	iommu_table_reserve_pages(tbl, res_start, res_end);
 
@@ -773,8 +770,6 @@ struct iommu_table *iommu_init_table(struct iommu_table *tbl, int nid,
 
 static void iommu_table_free(struct kref *kref)
 {
-	unsigned long bitmap_sz;
-	unsigned int order;
 	struct iommu_table *tbl;
 
 	tbl = container_of(kref, struct iommu_table, it_kref);
@@ -795,12 +790,8 @@ static void iommu_table_free(struct kref *kref)
 	if (!bitmap_empty(tbl->it_map, tbl->it_size))
 		pr_warn("%s: Unexpected TCEs\n", __func__);
 
-	/* calculate bitmap size in bytes */
-	bitmap_sz = BITS_TO_LONGS(tbl->it_size) * sizeof(unsigned long);
-
 	/* free bitmap */
-	order = get_order(bitmap_sz);
-	free_pages((unsigned long) tbl->it_map, order);
+	vfree(tbl->it_map);
 
 	/* free table */
 	kfree(tbl);