mm/hmm: add a helper function that fault pages and map them to a device (55c0ece8) · Commits · 戴 / test

include/linux/hmm.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -474,6 +474,15 @@ int hmm_range_register(struct hmm_range *range,
		void hmm_range_unregister(struct hmm_range *range);
		long hmm_range_snapshot(struct hmm_range *range);
		long hmm_range_fault(struct hmm_range *range, bool block);
		long hmm_range_dma_map(struct hmm_range *range,
		struct device *device,
		dma_addr_t *daddrs,
		bool block);
		long hmm_range_dma_unmap(struct hmm_range *range,
		struct vm_area_struct *vma,
		struct device *device,
		dma_addr_t *daddrs,
		bool dirty);

		/*
		* HMM_RANGE_DEFAULT_TIMEOUT - default timeout (ms) when waiting for a range

mm/hmm.c

+152 −0

Original line number	Diff line number	Diff line
		@@ -30,6 +30,7 @@
		#include <linux/hugetlb.h>
		#include <linux/memremap.h>
		#include <linux/jump_label.h>
		#include <linux/dma-mapping.h>
		#include <linux/mmu_notifier.h>
		#include <linux/memory_hotplug.h>

		@@ -1182,6 +1183,157 @@ long hmm_range_fault(struct hmm_range *range, bool block)
		return (hmm_vma_walk.last - range->start) >> PAGE_SHIFT;
		}
		EXPORT_SYMBOL(hmm_range_fault);

		/**
		* hmm_range_dma_map() - hmm_range_fault() and dma map page all in one.
		* @range: range being faulted
		* @device: device against to dma map page to
		* @daddrs: dma address of mapped pages
		* @block: allow blocking on fault (if true it sleeps and do not drop mmap_sem)
		* Returns: number of pages mapped on success, -EAGAIN if mmap_sem have been
		* drop and you need to try again, some other error value otherwise
		*
		* Note same usage pattern as hmm_range_fault().
		*/
		long hmm_range_dma_map(struct hmm_range *range,
		struct device *device,
		dma_addr_t *daddrs,
		bool block)
		{
		unsigned long i, npages, mapped;
		long ret;

		ret = hmm_range_fault(range, block);
		if (ret <= 0)
		return ret ? ret : -EBUSY;

		npages = (range->end - range->start) >> PAGE_SHIFT;
		for (i = 0, mapped = 0; i < npages; ++i) {
		enum dma_data_direction dir = DMA_TO_DEVICE;
		struct page *page;

		/*
		* FIXME need to update DMA API to provide invalid DMA address
		* value instead of a function to test dma address value. This
		* would remove lot of dumb code duplicated accross many arch.
		*
		* For now setting it to 0 here is good enough as the pfns[]
		* value is what is use to check what is valid and what isn't.
		*/
		daddrs[i] = 0;

		page = hmm_pfn_to_page(range, range->pfns[i]);
		if (page == NULL)
		continue;

		/* Check if range is being invalidated */
		if (!range->valid) {
		ret = -EBUSY;
		goto unmap;
		}

		/* If it is read and write than map bi-directional. */
		if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
		dir = DMA_BIDIRECTIONAL;

		daddrs[i] = dma_map_page(device, page, 0, PAGE_SIZE, dir);
		if (dma_mapping_error(device, daddrs[i])) {
		ret = -EFAULT;
		goto unmap;
		}

		mapped++;
		}

		return mapped;

		unmap:
		for (npages = i, i = 0; (i < npages) && mapped; ++i) {
		enum dma_data_direction dir = DMA_TO_DEVICE;
		struct page *page;

		page = hmm_pfn_to_page(range, range->pfns[i]);
		if (page == NULL)
		continue;

		if (dma_mapping_error(device, daddrs[i]))
		continue;

		/* If it is read and write than map bi-directional. */
		if (range->pfns[i] & range->flags[HMM_PFN_WRITE])
		dir = DMA_BIDIRECTIONAL;

		dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
		mapped--;
		}

		return ret;
		}
		EXPORT_SYMBOL(hmm_range_dma_map);

		/**
		* hmm_range_dma_unmap() - unmap range of that was map with hmm_range_dma_map()
		* @range: range being unmapped
		* @vma: the vma against which the range (optional)
		* @device: device against which dma map was done
		* @daddrs: dma address of mapped pages
		* @dirty: dirty page if it had the write flag set
		* Returns: number of page unmapped on success, -EINVAL otherwise
		*
		* Note that caller MUST abide by mmu notifier or use HMM mirror and abide
		* to the sync_cpu_device_pagetables() callback so that it is safe here to
		* call set_page_dirty(). Caller must also take appropriate locks to avoid
		* concurrent mmu notifier or sync_cpu_device_pagetables() to make progress.
		*/
		long hmm_range_dma_unmap(struct hmm_range *range,
		struct vm_area_struct *vma,
		struct device *device,
		dma_addr_t *daddrs,
		bool dirty)
		{
		unsigned long i, npages;
		long cpages = 0;

		/* Sanity check. */
		if (range->end <= range->start)
		return -EINVAL;
		if (!daddrs)
		return -EINVAL;
		if (!range->pfns)
		return -EINVAL;

		npages = (range->end - range->start) >> PAGE_SHIFT;
		for (i = 0; i < npages; ++i) {
		enum dma_data_direction dir = DMA_TO_DEVICE;
		struct page *page;

		page = hmm_pfn_to_page(range, range->pfns[i]);
		if (page == NULL)
		continue;

		/* If it is read and write than map bi-directional. */
		if (range->pfns[i] & range->flags[HMM_PFN_WRITE]) {
		dir = DMA_BIDIRECTIONAL;

		/*
		* See comments in function description on why it is
		* safe here to call set_page_dirty()
		*/
		if (dirty)
		set_page_dirty(page);
		}

		/* Unmap and clear pfns/dma address */
		dma_unmap_page(device, daddrs[i], PAGE_SIZE, dir);
		range->pfns[i] = range->values[HMM_PFN_NONE];
		/* FIXME see comments in hmm_vma_dma_map() */
		daddrs[i] = 0;
		cpages++;
		}

		return cpages;
		}
		EXPORT_SYMBOL(hmm_range_dma_unmap);
		#endif /* IS_ENABLED(CONFIG_HMM_MIRROR) */

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