xref: /openbmc/linux/drivers/xen/swiotlb-xen.c (revision 2a598d0b)
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *  Copyright 2010
4  *  by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
5  *
6  * This code provides a IOMMU for Xen PV guests with PCI passthrough.
7  *
8  * PV guests under Xen are running in an non-contiguous memory architecture.
9  *
10  * When PCI pass-through is utilized, this necessitates an IOMMU for
11  * translating bus (DMA) to virtual and vice-versa and also providing a
12  * mechanism to have contiguous pages for device drivers operations (say DMA
13  * operations).
14  *
15  * Specifically, under Xen the Linux idea of pages is an illusion. It
16  * assumes that pages start at zero and go up to the available memory. To
17  * help with that, the Linux Xen MMU provides a lookup mechanism to
18  * translate the page frame numbers (PFN) to machine frame numbers (MFN)
19  * and vice-versa. The MFN are the "real" frame numbers. Furthermore
20  * memory is not contiguous. Xen hypervisor stitches memory for guests
21  * from different pools, which means there is no guarantee that PFN==MFN
22  * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
23  * allocated in descending order (high to low), meaning the guest might
24  * never get any MFN's under the 4GB mark.
25  */
26 
27 #define pr_fmt(fmt) "xen:" KBUILD_MODNAME ": " fmt
28 
29 #include <linux/memblock.h>
30 #include <linux/dma-direct.h>
31 #include <linux/dma-map-ops.h>
32 #include <linux/export.h>
33 #include <xen/swiotlb-xen.h>
34 #include <xen/page.h>
35 #include <xen/xen-ops.h>
36 #include <xen/hvc-console.h>
37 
38 #include <asm/dma-mapping.h>
39 
40 #include <trace/events/swiotlb.h>
41 #define MAX_DMA_BITS 32
42 
43 /*
44  * Quick lookup value of the bus address of the IOTLB.
45  */
46 
47 static inline phys_addr_t xen_phys_to_bus(struct device *dev, phys_addr_t paddr)
48 {
49 	unsigned long bfn = pfn_to_bfn(XEN_PFN_DOWN(paddr));
50 	phys_addr_t baddr = (phys_addr_t)bfn << XEN_PAGE_SHIFT;
51 
52 	baddr |= paddr & ~XEN_PAGE_MASK;
53 	return baddr;
54 }
55 
56 static inline dma_addr_t xen_phys_to_dma(struct device *dev, phys_addr_t paddr)
57 {
58 	return phys_to_dma(dev, xen_phys_to_bus(dev, paddr));
59 }
60 
61 static inline phys_addr_t xen_bus_to_phys(struct device *dev,
62 					  phys_addr_t baddr)
63 {
64 	unsigned long xen_pfn = bfn_to_pfn(XEN_PFN_DOWN(baddr));
65 	phys_addr_t paddr = (xen_pfn << XEN_PAGE_SHIFT) |
66 			    (baddr & ~XEN_PAGE_MASK);
67 
68 	return paddr;
69 }
70 
71 static inline phys_addr_t xen_dma_to_phys(struct device *dev,
72 					  dma_addr_t dma_addr)
73 {
74 	return xen_bus_to_phys(dev, dma_to_phys(dev, dma_addr));
75 }
76 
77 static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
78 {
79 	unsigned long next_bfn, xen_pfn = XEN_PFN_DOWN(p);
80 	unsigned int i, nr_pages = XEN_PFN_UP(xen_offset_in_page(p) + size);
81 
82 	next_bfn = pfn_to_bfn(xen_pfn);
83 
84 	for (i = 1; i < nr_pages; i++)
85 		if (pfn_to_bfn(++xen_pfn) != ++next_bfn)
86 			return 1;
87 
88 	return 0;
89 }
90 
91 static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
92 {
93 	unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
94 	unsigned long xen_pfn = bfn_to_local_pfn(bfn);
95 	phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT;
96 
97 	/* If the address is outside our domain, it CAN
98 	 * have the same virtual address as another address
99 	 * in our domain. Therefore _only_ check address within our domain.
100 	 */
101 	if (pfn_valid(PFN_DOWN(paddr)))
102 		return is_swiotlb_buffer(dev, paddr);
103 	return 0;
104 }
105 
106 #ifdef CONFIG_X86
107 int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
108 {
109 	int rc;
110 	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);
111 	unsigned int i, dma_bits = order + PAGE_SHIFT;
112 	dma_addr_t dma_handle;
113 	phys_addr_t p = virt_to_phys(buf);
114 
115 	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));
116 	BUG_ON(nslabs % IO_TLB_SEGSIZE);
117 
118 	i = 0;
119 	do {
120 		do {
121 			rc = xen_create_contiguous_region(
122 				p + (i << IO_TLB_SHIFT), order,
123 				dma_bits, &dma_handle);
124 		} while (rc && dma_bits++ < MAX_DMA_BITS);
125 		if (rc)
126 			return rc;
127 
128 		i += IO_TLB_SEGSIZE;
129 	} while (i < nslabs);
130 	return 0;
131 }
132 
133 static void *
134 xen_swiotlb_alloc_coherent(struct device *dev, size_t size,
135 		dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs)
136 {
137 	u64 dma_mask = dev->coherent_dma_mask;
138 	int order = get_order(size);
139 	phys_addr_t phys;
140 	void *ret;
141 
142 	/* Align the allocation to the Xen page size */
143 	size = 1UL << (order + XEN_PAGE_SHIFT);
144 
145 	ret = (void *)__get_free_pages(flags, get_order(size));
146 	if (!ret)
147 		return ret;
148 	phys = virt_to_phys(ret);
149 
150 	*dma_handle = xen_phys_to_dma(dev, phys);
151 	if (*dma_handle + size - 1 > dma_mask ||
152 	    range_straddles_page_boundary(phys, size)) {
153 		if (xen_create_contiguous_region(phys, order, fls64(dma_mask),
154 				dma_handle) != 0)
155 			goto out_free_pages;
156 		SetPageXenRemapped(virt_to_page(ret));
157 	}
158 
159 	memset(ret, 0, size);
160 	return ret;
161 
162 out_free_pages:
163 	free_pages((unsigned long)ret, get_order(size));
164 	return NULL;
165 }
166 
167 static void
168 xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr,
169 		dma_addr_t dma_handle, unsigned long attrs)
170 {
171 	phys_addr_t phys = virt_to_phys(vaddr);
172 	int order = get_order(size);
173 
174 	/* Convert the size to actually allocated. */
175 	size = 1UL << (order + XEN_PAGE_SHIFT);
176 
177 	if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) ||
178 	    WARN_ON_ONCE(range_straddles_page_boundary(phys, size)))
179 	    	return;
180 
181 	if (TestClearPageXenRemapped(virt_to_page(vaddr)))
182 		xen_destroy_contiguous_region(phys, order);
183 	free_pages((unsigned long)vaddr, get_order(size));
184 }
185 #endif /* CONFIG_X86 */
186 
187 /*
188  * Map a single buffer of the indicated size for DMA in streaming mode.  The
189  * physical address to use is returned.
190  *
191  * Once the device is given the dma address, the device owns this memory until
192  * either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed.
193  */
194 static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
195 				unsigned long offset, size_t size,
196 				enum dma_data_direction dir,
197 				unsigned long attrs)
198 {
199 	phys_addr_t map, phys = page_to_phys(page) + offset;
200 	dma_addr_t dev_addr = xen_phys_to_dma(dev, phys);
201 
202 	BUG_ON(dir == DMA_NONE);
203 	/*
204 	 * If the address happens to be in the device's DMA window,
205 	 * we can safely return the device addr and not worry about bounce
206 	 * buffering it.
207 	 */
208 	if (dma_capable(dev, dev_addr, size, true) &&
209 	    !range_straddles_page_boundary(phys, size) &&
210 		!xen_arch_need_swiotlb(dev, phys, dev_addr) &&
211 		!is_swiotlb_force_bounce(dev))
212 		goto done;
213 
214 	/*
215 	 * Oh well, have to allocate and map a bounce buffer.
216 	 */
217 	trace_swiotlb_bounced(dev, dev_addr, size);
218 
219 	map = swiotlb_tbl_map_single(dev, phys, size, size, 0, dir, attrs);
220 	if (map == (phys_addr_t)DMA_MAPPING_ERROR)
221 		return DMA_MAPPING_ERROR;
222 
223 	phys = map;
224 	dev_addr = xen_phys_to_dma(dev, map);
225 
226 	/*
227 	 * Ensure that the address returned is DMA'ble
228 	 */
229 	if (unlikely(!dma_capable(dev, dev_addr, size, true))) {
230 		swiotlb_tbl_unmap_single(dev, map, size, dir,
231 				attrs | DMA_ATTR_SKIP_CPU_SYNC);
232 		return DMA_MAPPING_ERROR;
233 	}
234 
235 done:
236 	if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
237 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr))))
238 			arch_sync_dma_for_device(phys, size, dir);
239 		else
240 			xen_dma_sync_for_device(dev, dev_addr, size, dir);
241 	}
242 	return dev_addr;
243 }
244 
245 /*
246  * Unmap a single streaming mode DMA translation.  The dma_addr and size must
247  * match what was provided for in a previous xen_swiotlb_map_page call.  All
248  * other usages are undefined.
249  *
250  * After this call, reads by the cpu to the buffer are guaranteed to see
251  * whatever the device wrote there.
252  */
253 static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
254 		size_t size, enum dma_data_direction dir, unsigned long attrs)
255 {
256 	phys_addr_t paddr = xen_dma_to_phys(hwdev, dev_addr);
257 
258 	BUG_ON(dir == DMA_NONE);
259 
260 	if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
261 		if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr))))
262 			arch_sync_dma_for_cpu(paddr, size, dir);
263 		else
264 			xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
265 	}
266 
267 	/* NOTE: We use dev_addr here, not paddr! */
268 	if (is_xen_swiotlb_buffer(hwdev, dev_addr))
269 		swiotlb_tbl_unmap_single(hwdev, paddr, size, dir, attrs);
270 }
271 
272 static void
273 xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
274 		size_t size, enum dma_data_direction dir)
275 {
276 	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
277 
278 	if (!dev_is_dma_coherent(dev)) {
279 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
280 			arch_sync_dma_for_cpu(paddr, size, dir);
281 		else
282 			xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
283 	}
284 
285 	if (is_xen_swiotlb_buffer(dev, dma_addr))
286 		swiotlb_sync_single_for_cpu(dev, paddr, size, dir);
287 }
288 
289 static void
290 xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
291 		size_t size, enum dma_data_direction dir)
292 {
293 	phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
294 
295 	if (is_xen_swiotlb_buffer(dev, dma_addr))
296 		swiotlb_sync_single_for_device(dev, paddr, size, dir);
297 
298 	if (!dev_is_dma_coherent(dev)) {
299 		if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
300 			arch_sync_dma_for_device(paddr, size, dir);
301 		else
302 			xen_dma_sync_for_device(dev, dma_addr, size, dir);
303 	}
304 }
305 
306 /*
307  * Unmap a set of streaming mode DMA translations.  Again, cpu read rules
308  * concerning calls here are the same as for swiotlb_unmap_page() above.
309  */
310 static void
311 xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
312 		enum dma_data_direction dir, unsigned long attrs)
313 {
314 	struct scatterlist *sg;
315 	int i;
316 
317 	BUG_ON(dir == DMA_NONE);
318 
319 	for_each_sg(sgl, sg, nelems, i)
320 		xen_swiotlb_unmap_page(hwdev, sg->dma_address, sg_dma_len(sg),
321 				dir, attrs);
322 
323 }
324 
325 static int
326 xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
327 		enum dma_data_direction dir, unsigned long attrs)
328 {
329 	struct scatterlist *sg;
330 	int i;
331 
332 	BUG_ON(dir == DMA_NONE);
333 
334 	for_each_sg(sgl, sg, nelems, i) {
335 		sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
336 				sg->offset, sg->length, dir, attrs);
337 		if (sg->dma_address == DMA_MAPPING_ERROR)
338 			goto out_unmap;
339 		sg_dma_len(sg) = sg->length;
340 	}
341 
342 	return nelems;
343 out_unmap:
344 	xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
345 	sg_dma_len(sgl) = 0;
346 	return -EIO;
347 }
348 
349 static void
350 xen_swiotlb_sync_sg_for_cpu(struct device *dev, struct scatterlist *sgl,
351 			    int nelems, enum dma_data_direction dir)
352 {
353 	struct scatterlist *sg;
354 	int i;
355 
356 	for_each_sg(sgl, sg, nelems, i) {
357 		xen_swiotlb_sync_single_for_cpu(dev, sg->dma_address,
358 				sg->length, dir);
359 	}
360 }
361 
362 static void
363 xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
364 			       int nelems, enum dma_data_direction dir)
365 {
366 	struct scatterlist *sg;
367 	int i;
368 
369 	for_each_sg(sgl, sg, nelems, i) {
370 		xen_swiotlb_sync_single_for_device(dev, sg->dma_address,
371 				sg->length, dir);
372 	}
373 }
374 
375 /*
376  * Return whether the given device DMA address mask can be supported
377  * properly.  For example, if your device can only drive the low 24-bits
378  * during bus mastering, then you would pass 0x00ffffff as the mask to
379  * this function.
380  */
381 static int
382 xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
383 {
384 	return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask;
385 }
386 
387 const struct dma_map_ops xen_swiotlb_dma_ops = {
388 #ifdef CONFIG_X86
389 	.alloc = xen_swiotlb_alloc_coherent,
390 	.free = xen_swiotlb_free_coherent,
391 #else
392 	.alloc = dma_direct_alloc,
393 	.free = dma_direct_free,
394 #endif
395 	.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
396 	.sync_single_for_device = xen_swiotlb_sync_single_for_device,
397 	.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
398 	.sync_sg_for_device = xen_swiotlb_sync_sg_for_device,
399 	.map_sg = xen_swiotlb_map_sg,
400 	.unmap_sg = xen_swiotlb_unmap_sg,
401 	.map_page = xen_swiotlb_map_page,
402 	.unmap_page = xen_swiotlb_unmap_page,
403 	.dma_supported = xen_swiotlb_dma_supported,
404 	.mmap = dma_common_mmap,
405 	.get_sgtable = dma_common_get_sgtable,
406 	.alloc_pages = dma_common_alloc_pages,
407 	.free_pages = dma_common_free_pages,
408 };
409