xen/grant-table: Allow allocating buffers suitable for DMA (9bdc7304) · Commits · 戴 / test

drivers/xen/Kconfig

+14 −0

Original line number	Diff line number	Diff line
		@@ -161,6 +161,20 @@ config XEN_GRANT_DEV_ALLOC
		to other domains. This can be used to implement frontend drivers
		or as part of an inter-domain shared memory channel.

		config XEN_GRANT_DMA_ALLOC
		bool "Allow allocating DMA capable buffers with grant reference module"
		depends on XEN && HAS_DMA
		help
		Extends grant table module API to allow allocating DMA capable
		buffers and mapping foreign grant references on top of it.
		The resulting buffer is similar to one allocated by the balloon
		driver in that proper memory reservation is made by
		({increase\|decrease}_reservation and VA mappings are updated if
		needed).
		This is useful for sharing foreign buffers with HW drivers which
		cannot work with scattered buffers provided by the balloon driver,
		but require DMAable memory instead.

		config SWIOTLB_XEN
		def_bool y
		select SWIOTLB

drivers/xen/grant-table.c

+97 −0

Original line number	Diff line number	Diff line
		@@ -45,6 +45,9 @@
		#include <linux/workqueue.h>
		#include <linux/ratelimit.h>
		#include <linux/moduleparam.h>
		#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
		#include <linux/dma-mapping.h>
		#endif

		#include <xen/xen.h>
		#include <xen/interface/xen.h>
		@@ -57,6 +60,7 @@
		#ifdef CONFIG_X86
		#include <asm/xen/cpuid.h>
		#endif
		#include <xen/mem-reservation.h>
		#include <asm/xen/hypercall.h>
		#include <asm/xen/interface.h>

		@@ -838,6 +842,99 @@ void gnttab_free_pages(int nr_pages, struct page **pages)
		}
		EXPORT_SYMBOL_GPL(gnttab_free_pages);

		#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
		/**
		* gnttab_dma_alloc_pages - alloc DMAable pages suitable for grant mapping into
		* @args: arguments to the function
		*/
		int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args)
		{
		unsigned long pfn, start_pfn;
		size_t size;
		int i, ret;

		size = args->nr_pages << PAGE_SHIFT;
		if (args->coherent)
		args->vaddr = dma_alloc_coherent(args->dev, size,
		&args->dev_bus_addr,
		GFP_KERNEL \| __GFP_NOWARN);
		else
		args->vaddr = dma_alloc_wc(args->dev, size,
		&args->dev_bus_addr,
		GFP_KERNEL \| __GFP_NOWARN);
		if (!args->vaddr) {
		pr_debug("Failed to allocate DMA buffer of size %zu\n", size);
		return -ENOMEM;
		}

		start_pfn = __phys_to_pfn(args->dev_bus_addr);
		for (pfn = start_pfn, i = 0; pfn < start_pfn + args->nr_pages;
		pfn++, i++) {
		struct page *page = pfn_to_page(pfn);

		args->pages[i] = page;
		args->frames[i] = xen_page_to_gfn(page);
		xenmem_reservation_scrub_page(page);
		}

		xenmem_reservation_va_mapping_reset(args->nr_pages, args->pages);

		ret = xenmem_reservation_decrease(args->nr_pages, args->frames);
		if (ret != args->nr_pages) {
		pr_debug("Failed to decrease reservation for DMA buffer\n");
		ret = -EFAULT;
		goto fail;
		}

		ret = gnttab_pages_set_private(args->nr_pages, args->pages);
		if (ret < 0)
		goto fail;

		return 0;

		fail:
		gnttab_dma_free_pages(args);
		return ret;
		}
		EXPORT_SYMBOL_GPL(gnttab_dma_alloc_pages);

		/**
		* gnttab_dma_free_pages - free DMAable pages
		* @args: arguments to the function
		*/
		int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args)
		{
		size_t size;
		int i, ret;

		gnttab_pages_clear_private(args->nr_pages, args->pages);

		for (i = 0; i < args->nr_pages; i++)
		args->frames[i] = page_to_xen_pfn(args->pages[i]);

		ret = xenmem_reservation_increase(args->nr_pages, args->frames);
		if (ret != args->nr_pages) {
		pr_debug("Failed to decrease reservation for DMA buffer\n");
		ret = -EFAULT;
		} else {
		ret = 0;
		}

		xenmem_reservation_va_mapping_update(args->nr_pages, args->pages,
		args->frames);

		size = args->nr_pages << PAGE_SHIFT;
		if (args->coherent)
		dma_free_coherent(args->dev, size,
		args->vaddr, args->dev_bus_addr);
		else
		dma_free_wc(args->dev, size,
		args->vaddr, args->dev_bus_addr);
		return ret;
		}
		EXPORT_SYMBOL_GPL(gnttab_dma_free_pages);
		#endif

		/* Handling of paged out grant targets (GNTST_eagain) */
		#define MAX_DELAY 256
		static inline void

include/xen/grant_table.h

+18 −0

Original line number	Diff line number	Diff line
		@@ -198,6 +198,24 @@ void gnttab_free_auto_xlat_frames(void);
		int gnttab_alloc_pages(int nr_pages, struct page **pages);
		void gnttab_free_pages(int nr_pages, struct page **pages);

		#ifdef CONFIG_XEN_GRANT_DMA_ALLOC
		struct gnttab_dma_alloc_args {
		/* Device for which DMA memory will be/was allocated. */
		struct device *dev;
		/* If set then DMA buffer is coherent and write-combine otherwise. */
		bool coherent;

		int nr_pages;
		struct page **pages;
		xen_pfn_t *frames;
		void *vaddr;
		dma_addr_t dev_bus_addr;
		};

		int gnttab_dma_alloc_pages(struct gnttab_dma_alloc_args *args);
		int gnttab_dma_free_pages(struct gnttab_dma_alloc_args *args);
		#endif

		int gnttab_pages_set_private(int nr_pages, struct page **pages);
		void gnttab_pages_clear_private(int nr_pages, struct page **pages);

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