From a8e8af35c9f4f75f981a95488c7066d31bac4bef Mon Sep 17 00:00:00 2001 From: Lianbo Jiang Date: Tue, 26 Jan 2021 19:53:36 +0800 Subject: [PATCH] dma-iommu: use static-key to minimize the impact in the fast-path Let's move out the is_kdump_kernel() check from iommu_dma_deferred_attach() to iommu_dma_init(), and use the static-key in the fast-path to minimize the impact in the normal case. Co-developed-by: Robin Murphy Signed-off-by: Lianbo Jiang Signed-off-by: Robin Murphy Link: https://lore.kernel.org/r/20210126115337.20068-2-lijiang@redhat.com Signed-off-by: Joerg Roedel --- drivers/iommu/dma-iommu.c | 17 +++++++++++------ 1 file changed, 11 insertions(+), 6 deletions(-) diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index 4078358ed66e..c80056f6c9f9 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -51,6 +51,8 @@ struct iommu_dma_cookie { struct iommu_domain *fq_domain; }; +static DEFINE_STATIC_KEY_FALSE(iommu_deferred_attach_enabled); + void iommu_dma_free_cpu_cached_iovas(unsigned int cpu, struct iommu_domain *domain) { @@ -383,9 +385,6 @@ static int iommu_dma_deferred_attach(struct device *dev, { const struct iommu_ops *ops = domain->ops; - if (!is_kdump_kernel()) - return 0; - if (unlikely(ops->is_attach_deferred && ops->is_attach_deferred(domain, dev))) return iommu_attach_device(domain, dev); @@ -535,7 +534,8 @@ static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys, size_t iova_off = iova_offset(iovad, phys); dma_addr_t iova; - if (unlikely(iommu_dma_deferred_attach(dev, domain))) + if (static_branch_unlikely(&iommu_deferred_attach_enabled) && + iommu_dma_deferred_attach(dev, domain)) return DMA_MAPPING_ERROR; size = iova_align(iovad, size + iova_off); @@ -693,7 +693,8 @@ static void *iommu_dma_alloc_remap(struct device *dev, size_t size, *dma_handle = DMA_MAPPING_ERROR; - if (unlikely(iommu_dma_deferred_attach(dev, domain))) + if (static_branch_unlikely(&iommu_deferred_attach_enabled) && + iommu_dma_deferred_attach(dev, domain)) return NULL; min_size = alloc_sizes & -alloc_sizes; @@ -976,7 +977,8 @@ static int iommu_dma_map_sg(struct device *dev, struct scatterlist *sg, unsigned long mask = dma_get_seg_boundary(dev); int i; - if (unlikely(iommu_dma_deferred_attach(dev, domain))) + if (static_branch_unlikely(&iommu_deferred_attach_enabled) && + iommu_dma_deferred_attach(dev, domain)) return 0; if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC)) @@ -1424,6 +1426,9 @@ void iommu_dma_compose_msi_msg(struct msi_desc *desc, static int iommu_dma_init(void) { + if (is_kdump_kernel()) + static_branch_enable(&iommu_deferred_attach_enabled); + return iova_cache_get(); } arch_initcall(iommu_dma_init);