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
26static gfp_t xen_swiotlb_gfp(void)
27{
28	phys_addr_t base;
29	u64 i;
30
31	for_each_mem_range(i, &base, NULL) {
32		if (base < (phys_addr_t)0xffffffff) {
33			if (IS_ENABLED(CONFIG_ZONE_DMA32))
34				return __GFP_DMA32;
35			return __GFP_DMA;
36		}
37	}
38
39	return GFP_KERNEL;
40}
41
42static bool hypercall_cflush = false;
43
44/* buffers in highmem or foreign pages cannot cross page boundaries */
45static void dma_cache_maint(struct device *dev, dma_addr_t handle,
46			    size_t size, u32 op)
47{
48	struct gnttab_cache_flush cflush;
49
50	cflush.offset = xen_offset_in_page(handle);
51	cflush.op = op;
52	handle &= XEN_PAGE_MASK;
53
54	do {
55		cflush.a.dev_bus_addr = dma_to_phys(dev, handle);
56
57		if (size + cflush.offset > XEN_PAGE_SIZE)
58			cflush.length = XEN_PAGE_SIZE - cflush.offset;
59		else
60			cflush.length = size;
61
62		HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1);
63
64		cflush.offset = 0;
65		handle += cflush.length;
66		size -= cflush.length;
67	} while (size);
68}
69
70/*
71 * Dom0 is mapped 1:1, and while the Linux page can span across multiple Xen
72 * pages, it is not possible for it to contain a mix of local and foreign Xen
73 * pages.  Calling pfn_valid on a foreign mfn will always return false, so if
74 * pfn_valid returns true the pages is local and we can use the native
75 * dma-direct functions, otherwise we call the Xen specific version.
76 */
77void xen_dma_sync_for_cpu(struct device *dev, dma_addr_t handle,
78			  size_t size, enum dma_data_direction dir)
79{
80	if (dir != DMA_TO_DEVICE)
81		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
82}
83
84void xen_dma_sync_for_device(struct device *dev, dma_addr_t handle,
85			     size_t size, enum dma_data_direction dir)
86{
87	if (dir == DMA_FROM_DEVICE)
88		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_INVAL);
89	else
90		dma_cache_maint(dev, handle, size, GNTTAB_CACHE_CLEAN);
91}
92
93bool xen_arch_need_swiotlb(struct device *dev,
94			   phys_addr_t phys,
95			   dma_addr_t dev_addr)
96{
97	unsigned int xen_pfn = XEN_PFN_DOWN(phys);
98	unsigned int bfn = XEN_PFN_DOWN(dma_to_phys(dev, dev_addr));
99
100	/*
101	 * The swiotlb buffer should be used if
102	 *	- Xen doesn't have the cache flush hypercall
103	 *	- The Linux page refers to foreign memory
104	 *	- The device doesn't support coherent DMA request
105	 *
106	 * The Linux page may be spanned acrros multiple Xen page, although
107	 * it's not possible to have a mix of local and foreign Xen page.
108	 * Furthermore, range_straddles_page_boundary is already checking
109	 * if buffer is physically contiguous in the host RAM.
110	 *
111	 * Therefore we only need to check the first Xen page to know if we
112	 * require a bounce buffer because the device doesn't support coherent
113	 * memory and we are not able to flush the cache.
114	 */
115	return (!hypercall_cflush && (xen_pfn != bfn) &&
116		!dev_is_dma_coherent(dev));
117}
118
119static int __init xen_mm_init(void)
120{
121	struct gnttab_cache_flush cflush;
122	int rc;
123
124	if (!xen_swiotlb_detect())
125		return 0;
126
127	/* we can work with the default swiotlb */
128	rc = swiotlb_init_late(swiotlb_size_or_default(),
129			       xen_swiotlb_gfp(), NULL);
130	if (rc < 0)
131		return rc;
132
133	cflush.op = 0;
134	cflush.a.dev_bus_addr = 0;
135	cflush.offset = 0;
136	cflush.length = 0;
137	if (HYPERVISOR_grant_table_op(GNTTABOP_cache_flush, &cflush, 1) != -ENOSYS)
138		hypercall_cflush = true;
139	return 0;
140}
141arch_initcall(xen_mm_init);
142