Re: [PATCH 1/2] dma-mapping: add a dma_ops_bypass flag to struct device
From: Aneesh Kumar K.V <hidden>
Date: 2020-03-23 15:38:04
Also in:
linux-iommu, lkml
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Christoph Hellwig [off-list ref] writes:
On Mon, Mar 23, 2020 at 09:37:05AM +0100, Christoph Hellwig wrote:quoted
quoted
quoted
+ /* + * Allows IOMMU drivers to bypass dynamic translations if the DMA mask + * is large enough. + */ + if (dev->dma_ops_bypass) { + if (min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit) >= + dma_direct_get_required_mask(dev)) + return true; + }Why not do this in dma_map_direct() as well?Mostly beacuse it is a relatively expensive operation, including a fls64.Which I guess isn't too bad compared to a dynamic IOMMU mapping. Can you just send a draft patch for what you'd like to see for ppc?
This is what I was trying, but considering I am new to DMA subsystem, I am not sure I got all the details correct. The idea is to look at the cpu addr and see if that can be used in direct map fashion(is bus_dma_limit the right restriction here?) if not fallback to dynamic IOMMU mapping.
diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index e486d1d78de2..bc7e6a8b2caa 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c@@ -31,6 +31,87 @@ static inline bool dma_iommu_map_bypass(struct device *dev, (!iommu_fixed_is_weak || (attrs & DMA_ATTR_WEAK_ORDERING)); } +static inline bool __dma_direct_map_capable(struct device *dev, struct page *page, + unsigned long offset, size_t size) +{ + phys_addr_t phys = page_to_phys(page) + offset; + dma_addr_t dma_addr = phys_to_dma(dev, phys); + dma_addr_t end = dma_addr + size - 1; + + return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit); +} + +static inline bool dma_direct_map_capable(struct device *dev, struct page *page, + unsigned long offset, size_t size, + unsigned long attrs) +{ + if (!dma_iommu_map_bypass(dev, attrs)) + return false; + + if (!dev->dma_mask) + return false; + + return __dma_direct_map_capable(dev, page, offset, size); +} + + +static inline bool dma_direct_unmap_capable(struct device *dev, dma_addr_t addr, size_t size, + unsigned long attrs) +{ + dma_addr_t end = addr + size - 1; + + if (!dma_iommu_map_bypass(dev, attrs)) + return false; + + if (!dev->dma_mask) + return false; + + return end <= min_not_zero(*dev->dma_mask, dev->bus_dma_limit); +} + +static inline bool dma_direct_sg_map_capable(struct device *dev, struct scatterlist *sglist, + int nelems, unsigned long attrs) +{ + int i; + struct scatterlist *sg; + + if (!dma_iommu_map_bypass(dev, attrs)) + return false; + + if (!dev->dma_mask) + return false; + + for_each_sg(sglist, sg, nelems, i) { + if (!__dma_direct_map_capable(dev, sg_page(sg), + sg->offset, sg->length)) + return false; + } + return true; +} + +static inline bool dma_direct_sg_unmap_capable(struct device *dev, struct scatterlist *sglist, + int nelems, unsigned long attrs) +{ + int i; + dma_addr_t end; + struct scatterlist *sg; + + if (!dma_iommu_map_bypass(dev, attrs)) + return false; + + if (!dev->dma_mask) + return false; + + for_each_sg(sglist, sg, nelems, i) { + end = sg->dma_address + sg_dma_len(sg); + + if (end > min_not_zero(*dev->dma_mask, dev->bus_dma_limit)) + return false; + } + return true; +} + + /* Allocates a contiguous real buffer and creates mappings over it. * Returns the virtual address of the buffer and sets dma_handle * to the dma address (mapping) of the first page.
@@ -67,7 +148,7 @@ static dma_addr_t dma_iommu_map_page(struct device *dev, struct page *page, enum dma_data_direction direction, unsigned long attrs) { - if (dma_iommu_map_bypass(dev, attrs)) + if (dma_direct_map_capable(dev, page, offset, size, attrs)) return dma_direct_map_page(dev, page, offset, size, direction, attrs); return iommu_map_page(dev, get_iommu_table_base(dev), page, offset,
@@ -79,7 +160,7 @@ static void dma_iommu_unmap_page(struct device *dev, dma_addr_t dma_handle, size_t size, enum dma_data_direction direction, unsigned long attrs) { - if (!dma_iommu_map_bypass(dev, attrs)) + if (!dma_direct_unmap_capable(dev, dma_handle, size, attrs)) iommu_unmap_page(get_iommu_table_base(dev), dma_handle, size, direction, attrs); else
@@ -91,7 +172,7 @@ static int dma_iommu_map_sg(struct device *dev, struct scatterlist *sglist, int nelems, enum dma_data_direction direction, unsigned long attrs) { - if (dma_iommu_map_bypass(dev, attrs)) + if (dma_direct_sg_map_capable(dev, sglist, nelems, attrs)) return dma_direct_map_sg(dev, sglist, nelems, direction, attrs); return ppc_iommu_map_sg(dev, get_iommu_table_base(dev), sglist, nelems, dma_get_mask(dev), direction, attrs);
@@ -101,7 +182,7 @@ static void dma_iommu_unmap_sg(struct device *dev, struct scatterlist *sglist, int nelems, enum dma_data_direction direction, unsigned long attrs) { - if (!dma_iommu_map_bypass(dev, attrs)) + if (!dma_direct_sg_unmap_capable(dev, sglist, nelems, attrs)) ppc_iommu_unmap_sg(get_iommu_table_base(dev), sglist, nelems, direction, attrs); else
diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 99f72162dd85..702a680f5766 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c@@ -1119,6 +1119,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn) spin_unlock(&direct_window_list_lock); dma_addr = be64_to_cpu(ddwprop->dma_base); + dev->dev.bus_dma_limit = dma_addr + query.largest_available_block; goto out_unlock; out_free_window: