[PATCH v4 1/4] iommu/iova: Avoid over-allocating when size-aligned
From: robin.murphy@arm.com (Robin Murphy)
Date: 2015-07-16 18:40:12
Also in:
linux-iommu
Subsystem:
iommu dma-api layer, iommu subsystem, the rest · Maintainers:
Robin Murphy, Joerg Roedel, Will Deacon, Linus Torvalds
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. CC: David Woodhouse <dwmw2@infradead.org> Signed-off-by: Robin Murphy <robin.murphy@arm.com> --- drivers/iommu/intel-iommu.c | 2 ++ drivers/iommu/iova.c | 23 ++++++----------------- 2 files changed, 8 insertions(+), 17 deletions(-)
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a98a7b2..9210159 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c@@ -3233,6 +3233,8 @@ static struct iova *intel_alloc_iova(struct device *dev, /* Restrict dma_mask to the width that the iommu can handle */ dma_mask = min_t(uint64_t, DOMAIN_MAX_ADDR(domain->gaw), dma_mask); + /* Ensure we reserve the whole size-aligned region */ + nrpages = __roundup_pow_of_two(nrpages); if (!dmar_forcedac && dma_mask > DMA_BIT_MASK(32)) { /*
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);
--
1.9.1