Re: [PATCH kernel 1/2] powerpc/iommu: Allocate it_map by vmalloc
From: Leonardo Bras <hidden>
Date: 2021-02-17 19:12:25
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 <redacted>
It looks a very good change, and also makes code much simpler to read. FWIW: Reviewed-by: Leonardo Bras <leobras.c@gmail,com>
quoted hunk ↗ jump to hunk
--- 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);