On Tue, 2021-02-16 at 14:33 +1100, Alexey Kardashevskiy wrote:
> 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 <a...@ozlabs.ru>
It looks a very good change, and also makes code much simpler to read.
FWIW:
Reviewed-by: Leonardo Bras <leobras.c@gmail,com>
> ---
> arch/powerpc/kernel/iommu.c | 15 +++------------
> 1 file changed, 3 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
> index c00214a4355c..8eb6eb0afa97 100644
> --- a/arch/powerpc/kernel/iommu.c
> +++ b/arch/powerpc/kernel/iommu.c
> @@ -719,7 +719,6 @@ 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;
>
>
>
>
> @@ -728,11 +727,9 @@ 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);
>
>
>
>
> @@ -774,8 +771,6 @@ 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);
> @@ -796,12 +791,8 @@ 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);
