From 8f6429c7cb59f28433253575cc8e3262eed63592 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Thu, 16 Jul 2015 19:40:12 +0100 Subject: iommu/iova: Avoid over-allocating when size-aligned Currently, allocating a size-aligned IOVA region quietly adjusts the actual allocation size in the process, returning a rounded-up power-of-two-sized allocation. This results in mismatched behaviour in the IOMMU driver if the original size was not a power of two, where the original size is mapped, but the rounded-up IOVA size is unmapped. Whilst some IOMMUs will happily unmap already-unmapped pages, others consider this an error, so fix it by computing the necessary alignment padding without altering the actual allocation size. Also clean up by making pad_size unsigned, since its callers always pass unsigned values and negative padding makes little sense here anyway. Signed-off-by: Robin Murphy Signed-off-by: David Woodhouse --- drivers/iommu/iova.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-) (limited to 'drivers/iommu/iova.c') diff --git a/drivers/iommu/iova.c b/drivers/iommu/iova.c index b7c3d92..29f2efc 100644 --- a/drivers/iommu/iova.c +++ b/drivers/iommu/iova.c @@ -120,19 +120,14 @@ __cached_rbnode_delete_update(struct iova_domain *iovad, struct iova *free) } } -/* Computes the padding size required, to make the - * the start address naturally aligned on its size +/* + * Computes the padding size required, to make the start address + * naturally aligned on the power-of-two order of its size */ -static int -iova_get_pad_size(int size, unsigned int limit_pfn) +static unsigned int +iova_get_pad_size(unsigned int size, unsigned int limit_pfn) { - unsigned int pad_size = 0; - unsigned int order = ilog2(size); - - if (order) - pad_size = (limit_pfn + 1) % (1 << order); - - return pad_size; + return (limit_pfn + 1 - size) & (__roundup_pow_of_two(size) - 1); } static int __alloc_and_insert_iova_range(struct iova_domain *iovad, @@ -265,12 +260,6 @@ alloc_iova(struct iova_domain *iovad, unsigned long size, if (!new_iova) return NULL; - /* If size aligned is set then round the size to - * to next power of two. - */ - if (size_aligned) - size = __roundup_pow_of_two(size); - ret = __alloc_and_insert_iova_range(iovad, size, limit_pfn, new_iova, size_aligned); -- cgit v1.1