path: root/kernel/dma/direct.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (C) 2018-2020 Christoph Hellwig.
 *
 * DMA operations that map physical memory directly without using an IOMMU.
 */
#include <linux/memblock.h> /* for max_pfn */
#include <linux/export.h>
#include <linux/mm.h>
#include <linux/dma-map-ops.h>
#include <linux/scatterlist.h>
#include <linux/pfn.h>
#include <linux/vmalloc.h>
#include <linux/set_memory.h>
#include <linux/slab.h>
#include "direct.h"

/*
 * Most architectures use ZONE_DMA for the first 16 Megabytes, but some use
 * it for entirely different regions. In that case the arch code needs to
 * override the variable below for dma-direct to work properly.
 */
unsigned int zone_dma_bits __ro_after_init = 24;

static inline dma_addr_t phys_to_dma_direct(struct device *dev,
		phys_addr_t phys)
{
	if (force_dma_unencrypted(dev))
		return phys_to_dma_unencrypted(dev, phys);
	return phys_to_dma(dev, phys);
}

static inline struct page *dma_direct_to_page(struct device *dev,
		dma_addr_t dma_addr)
{
	return pfn_to_page(PHYS_PFN(dma_to_phys(dev, dma_addr)));
}

u64 dma_direct_get_required_mask(struct device *dev)
{
	phys_addr_t phys = (phys_addr_t)(max_pfn - 1) << PAGE_SHIFT;
	u64 max_dma = phys_to_dma_direct(dev, phys);

	return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
}

static gfp_t dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask,
				  u64 *phys_limit)
{
	u64 dma_limit = min_not_zero(dma_mask, dev->bus_dma_limit);

	/*
	 * Optimistically try the zone that the physical address mask falls
	 * into first.  If that returns memory that isn't actually addressable
	 * we will fallback to the next lower zone and try again.
	 *
	 * Note that GFP_DMA32 and GFP_DMA are no ops without the corresponding
	 * zones.
	 */
	*phys_limit = dma_to_phys(dev, dma_limit);
	if (*phys_limit <= DMA_BIT_MASK(zone_dma_bits))
		return GFP_DMA;
	if (*phys_limit <= DMA_BIT_MASK(32))
		return GFP_DMA32;
	return 0;
}

static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size)
{
	dma_addr_t dma_addr = phys_to_dma_direct(dev, phys);

	if (dma_addr == DMA_MAPPING_ERROR)
		return false;
	return dma_addr + size - 1 <=
		min_not_zero(dev->coherent_dma_mask, dev->bus_dma_limit);
}

static struct page *__dma_direct_alloc_pages(struct device *dev, size_t size,
		gfp_t gfp)
{
	int node = dev_to_node(dev);
	struct page *page = NULL;
	u64 phys_limit;

	WARN_ON_ONCE(!PAGE_ALIGNED(size));

	gfp |= dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
					   &phys_limit);
	page = dma_alloc_contiguous(dev, size, gfp);
	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
		dma_free_contiguous(dev, page, size);
		page = NULL;
	}
again:
	if (!page)
		page = alloc_pages_node(node, gfp, get_order(size));
	if (page && !dma_coherent_ok(dev, page_to_phys(page), size)) {
		dma_free_contiguous(dev, page, size);
		page = NULL;

		if (IS_ENABLED(CONFIG_ZONE_DMA32) &&
		    phys_limit < DMA_BIT_MASK(64) &&
		    !(gfp & (GFP_DMA32 | GFP_DMA))) {
			gfp |= GFP_DMA32;
			goto again;
		}

		if (IS_ENABLED(CONFIG_ZONE_DMA) && !(gfp & GFP_DMA)) {
			gfp = (gfp & ~GFP_DMA32) | GFP_DMA;
			goto again;
		}
	}

	return page;
}

static void *dma_direct_alloc_from_pool(struct device *dev, size_t size,
		dma_addr_t *dma_handle, gfp_t gfp)
{
	struct page *page;
	u64 phys_mask;
	void *ret;

	gfp |= dma_direct_optimal_gfp_mask(dev, dev->coherent_dma_mask,
					   &phys_mask);
	page = dma_alloc_from_pool(dev, size, &ret, gfp, dma_coherent_ok);
	if (!page)
		return NULL;
	*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
	return ret;
}

void *dma_direct_alloc(struct device *dev, size_t size,
		dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
{
	struct page *page;
	void *ret;
	int err;

	size = PAGE_ALIGN(size);
	if (attrs & DMA_ATTR_NO_WARN)
		gfp |= __GFP_NOWARN;

	if ((attrs & DMA_ATTR_NO_KERNEL_MAPPING) &&
	    !force_dma_unencrypted(dev)) {
		page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
		if (!page)
			return NULL;
		/* remove any dirty cache lines on the kernel alias */
		if (!PageHighMem(page))
			arch_dma_prep_coherent(page, size);
		*dma_handle = phys_to_dma_direct(dev, page_to_phys(page));
		/* return the page pointer as the opaque cookie */
		return page;
	}

	if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_SET_UNCACHED) &&
	    !IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
	    !dev_is_dma_coherent(dev))
		return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);

	/*
	 * Remapping or decrypting memory may block. If either is required and
	 * we can't block, allocate the memory from the atomic pools.
	 */
	if (IS_ENABLED(CONFIG_DMA_COHERENT_POOL) &&
	    !gfpflags_allow_blocking(gfp) &&
	    (force_dma_unencrypted(dev) ||
	     (IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) && !dev_is_dma_coherent(dev))))
		return dma_direct_alloc_from_pool(dev, size, dma_handle, gfp);

	/* we always manually zero the memory once we are done */
	page = __dma_direct_alloc_pages(dev, size, gfp & ~__GFP_ZERO);
	if (!page)
		return NULL;

	if ((IS_ENABLED(CONFIG_DMA_DIRECT_REMAP) &&
	     !dev_is_dma_coherent(dev)) ||
	    (IS_ENABLED(CONFIG_DMA_REMAP) && PageHighMem(page))) {
		/* remove any dirty cache lines on the kernel alias */
		arch_dma_prep_coherent(page, size);

		/* create a coherent mapping */
		ret = dma_common_contiguous_remap(page, size,
				dma_pgprot(dev, PAGE_KERNEL, attrs),
				__builtin_return_address(0));
		if (!ret)
			goto out_free_pages;
		if (force_dma_unencrypted(dev)) {
			err = set_memory_decrypted((unsigned long)ret,
						   1 << get_order(size));
			if (err)
				goto out_free_pages;
		}
		memset(ret, 0, size);
		goto done;
	}

	if (PageHighMem(page)) {
		/*
		 * Depending on the cma= arguments and per-arch setup
		 * dma_alloc_contiguous could return highmem pages.
		 * Without remapping there is no way to return them here,
		 * so log an error and fail.
		 */
		dev_info(dev, "Rejecting highmem page from CMA.\n");
		goto out_free_pages;
	}

	ret = page_address(page);
	if (force_dma_unencrypted(dev)) {
		err = set_memory_decrypted((unsigned long)ret,
					   1 << get_order(size));
		if (err)
			goto out_free_pages;