1// SPDX-License-Identifier: GPL-2.0-only
  2#include <linux/cpu.h>
  3#include <linux/dma-direct.h>
  4#include <linux/dma-map-ops.h>
  5#include <linux/gfp.h>
  6#include <linux/highmem.h>
  7#include <linux/export.h>
  8#include <linux/memblock.h>
  9#include <linux/of_address.h>
 10#include <linux/slab.h>
 11#include <linux/types.h>
 12#include <linux/vmalloc.h>
 13#include <linux/swiotlb.h>
 14
 15#include <xen/xen.h>
 16#include <xen/interface/grant_table.h>
 17#include <xen/interface/memory.h>
 18#include <xen/page.h>
 19#include <xen/xen-ops.h>
 20#include <xen/swiotlb-xen.h>
 21
 22#include <asm/cacheflush.h>
 23#include <asm/xen/hypercall.h>
 24#include <asm/xen/interface.h>
 25
 26unsigned long xen_get_swiotlb_free_pages(unsigned int order)
 27{
 28	phys_addr_t base;
 29	gfp_t flags = __GFP_NOWARN|__GFP_KSWAPD_RECLAIM;
 30	u64 i;
 31
 32	for_each_mem_range(i, &base, NULL) {
 33		if (base < (phys_addr_t)0xffffffff) {
 34			if (IS_ENABLED(CONFIG_ZONE_DMA32))
 35				flags |= __GFP_DMA32;
 36			else
 37				flags |= __GFP_DMA;
 38			break;
 39		}
 40	}
 41	return __get_free_pages(flags, order);
 42}
 43
 44static bool hypercall_cflush = false;
 45
 46/* buffers in highmem or foreign pages cannot cross page boundaries */
 47static void dma_cache_maint(struct device *dev, dma_addr_t handle,
 48			    size_t size, u32 op)
 49{
 50	struct gnttab_cache_flush cflush;
 51
 52	cflush.offset = xen_offset_in_page(handle);
 53	cflush.op = op;
 54	handle &= XEN_PAGE_MASK;
 55
 56	do {
 57		cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
 58
 59		if (size + cflush.offset > XEN_PAGE_SIZE)
 60			cflush.length = XEN_PAGE_SIZE - cflush.offset;
 61		else
 62			cflush.length = size;
 63
 64		HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
 65
 66		cflush.offset = 0;
 67		handle += cflush.length;
 68		size -= cflush.length;
 69	} while (size);
 70}
 71
 72/*
 73 * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
 74 * pages, it is not possible for it to contain a mix of local and foreign Xen
 75 * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
 76 * pfn_valid returns true the pages is local and we can use the native
 77 * dma-direct functions, otherwise we call the Xen specific version.
 78 */
 79void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
 80			  size_t size, enum dma_data_direction dir)
 81{
 82	if (dir != DMA_TO_DEVICE)
 83		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
 84}
 85
 86void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
 87			     size_t size, enum dma_data_direction dir)
 88{
 89	if (dir == DMA_FROM_DEVICE)
 90		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
 91	else
 92		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
 93}
 94
 95bool xen_arch_need_swiotlb(struct device *dev,
 96			   phys_addr_t phys,
 97			   dma_addr_t dev_addr)
 98{
 99	unsigned int xen_pfn = XEN_PFN_DOWN(phys);
100	unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr));
101
102	/*
103	 * The swiotlb buffer should be used if
104	 *	- Xen doesn't have the cache flush hypercall
105	 *	- The Linux page refers to foreign memory
106	 *	- The device doesn't support coherent DMA request
107	 *
108	 * The Linux page may be spanned acrros multiple Xen page, although
109	 * it's not possible to have a mix of local and foreign Xen page.
110	 * Furthermore, range_straddles_page_boundary is already checking
111	 * if buffer is physically contiguous in the host RAM.
112	 *
113	 * Therefore we only need to check the first Xen page to know if we
114	 * require a bounce buffer because the device doesn't support coherent
115	 * memory and we are not able to flush the cache.
116	 */
117	return (!hypercall_cflush && (xen_pfn != bfn) &&
118		!dev_is_dma_coherent(dev));
119}
120
121int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
122				 unsigned int address_bits,
123				 dma_addr_t *dma_handle)
124{
125	if (!xen_initial_domain())
126		return -EINVAL;
127
128	/* we assume that dom0 is mapped 1:1 for now */
129	*dma_handle = pstart;
130	return 0;
131}
132
133void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
134{
135	return;
136}
137
138static int __init xen_mm_init(void)
139{
140	struct gnttab_cache_flush cflush;
141	int rc;
142
143	if (!xen_swiotlb_detect())
144		return 0;
145
146	rc = xen_swiotlb_init();
147	/* we can work with the default swiotlb */
148	if (rc < 0 && rc != -EEXIST)
149		return rc;
150
151	cflush.op = 0;
152	cflush.a.dev_bus_addr = 0;
153	cflush.offset = 0;
154	cflush.length = 0;
155	if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
156		hypercall_cflush = true;
157	return 0;
158}
159arch_initcall(xen_mm_init);