Commit 7f1fa82d authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Michael Ellerman
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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: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210216033307.69863-2-aik@ozlabs.ru
parent 0db11461

arch/powerpc/kernel/iommu.c

+3 −12
Original line number Diff line number Diff line
@@ -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);