Root/drivers/xen/swiotlb-xen.c

1/*
2 * Copyright 2010
3 * by Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
4 *
5 * This code provides a IOMMU for Xen PV guests with PCI passthrough.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License v2.0 as published by
9 * the Free Software Foundation
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * PV guests under Xen are running in an non-contiguous memory architecture.
17 *
18 * When PCI pass-through is utilized, this necessitates an IOMMU for
19 * translating bus (DMA) to virtual and vice-versa and also providing a
20 * mechanism to have contiguous pages for device drivers operations (say DMA
21 * operations).
22 *
23 * Specifically, under Xen the Linux idea of pages is an illusion. It
24 * assumes that pages start at zero and go up to the available memory. To
25 * help with that, the Linux Xen MMU provides a lookup mechanism to
26 * translate the page frame numbers (PFN) to machine frame numbers (MFN)
27 * and vice-versa. The MFN are the "real" frame numbers. Furthermore
28 * memory is not contiguous. Xen hypervisor stitches memory for guests
29 * from different pools, which means there is no guarantee that PFN==MFN
30 * and PFN+1==MFN+1. Lastly with Xen 4.0, pages (in debug mode) are
31 * allocated in descending order (high to low), meaning the guest might
32 * never get any MFN's under the 4GB mark.
33 *
34 */
35
36#include <linux/bootmem.h>
37#include <linux/dma-mapping.h>
38#include <linux/export.h>
39#include <xen/swiotlb-xen.h>
40#include <xen/page.h>
41#include <xen/xen-ops.h>
42#include <xen/hvc-console.h>
43/*
44 * Used to do a quick range check in swiotlb_tbl_unmap_single and
45 * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this
46 * API.
47 */
48
49static char *xen_io_tlb_start, *xen_io_tlb_end;
50static unsigned long xen_io_tlb_nslabs;
51/*
52 * Quick lookup value of the bus address of the IOTLB.
53 */
54
55u64 start_dma_addr;
56
57static dma_addr_t xen_phys_to_bus(phys_addr_t paddr)
58{
59    return phys_to_machine(XPADDR(paddr)).maddr;
60}
61
62static phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
63{
64    return machine_to_phys(XMADDR(baddr)).paddr;
65}
66
67static dma_addr_t xen_virt_to_bus(void *address)
68{
69    return xen_phys_to_bus(virt_to_phys(address));
70}
71
72static int check_pages_physically_contiguous(unsigned long pfn,
73                         unsigned int offset,
74                         size_t length)
75{
76    unsigned long next_mfn;
77    int i;
78    int nr_pages;
79
80    next_mfn = pfn_to_mfn(pfn);
81    nr_pages = (offset + length + PAGE_SIZE-1) >> PAGE_SHIFT;
82
83    for (i = 1; i < nr_pages; i++) {
84        if (pfn_to_mfn(++pfn) != ++next_mfn)
85            return 0;
86    }
87    return 1;
88}
89
90static int range_straddles_page_boundary(phys_addr_t p, size_t size)
91{
92    unsigned long pfn = PFN_DOWN(p);
93    unsigned int offset = p & ~PAGE_MASK;
94
95    if (offset + size <= PAGE_SIZE)
96        return 0;
97    if (check_pages_physically_contiguous(pfn, offset, size))
98        return 0;
99    return 1;
100}
101
102static int is_xen_swiotlb_buffer(dma_addr_t dma_addr)
103{
104    unsigned long mfn = PFN_DOWN(dma_addr);
105    unsigned long pfn = mfn_to_local_pfn(mfn);
106    phys_addr_t paddr;
107
108    /* If the address is outside our domain, it CAN
109     * have the same virtual address as another address
110     * in our domain. Therefore _only_ check address within our domain.
111     */
112    if (pfn_valid(pfn)) {
113        paddr = PFN_PHYS(pfn);
114        return paddr >= virt_to_phys(xen_io_tlb_start) &&
115               paddr < virt_to_phys(xen_io_tlb_end);
116    }
117    return 0;
118}
119
120static int max_dma_bits = 32;
121
122static int
123xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs)
124{
125    int i, rc;
126    int dma_bits;
127
128    dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;
129
130    i = 0;
131    do {
132        int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);
133
134        do {
135            rc = xen_create_contiguous_region(
136                (unsigned long)buf + (i << IO_TLB_SHIFT),
137                get_order(slabs << IO_TLB_SHIFT),
138                dma_bits);
139        } while (rc && dma_bits++ < max_dma_bits);
140        if (rc)
141            return rc;
142
143        i += slabs;
144    } while (i < nslabs);
145    return 0;
146}
147
148void __init xen_swiotlb_init(int verbose)
149{
150    unsigned long bytes;
151    int rc = -ENOMEM;
152    unsigned long nr_tbl;
153    char *m = NULL;
154    unsigned int repeat = 3;
155
156    nr_tbl = swiotlb_nr_tbl();
157    if (nr_tbl)
158        xen_io_tlb_nslabs = nr_tbl;
159    else {
160        xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT);
161        xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE);
162    }
163retry:
164    bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT;
165
166    /*
167     * Get IO TLB memory from any location.
168     */
169    xen_io_tlb_start = alloc_bootmem_pages(PAGE_ALIGN(bytes));
170    if (!xen_io_tlb_start) {
171        m = "Cannot allocate Xen-SWIOTLB buffer!\n";
172        goto error;
173    }
174    xen_io_tlb_end = xen_io_tlb_start + bytes;
175    /*
176     * And replace that memory with pages under 4GB.
177     */
178    rc = xen_swiotlb_fixup(xen_io_tlb_start,
179                   bytes,
180                   xen_io_tlb_nslabs);
181    if (rc) {
182        free_bootmem(__pa(xen_io_tlb_start), PAGE_ALIGN(bytes));
183        m = "Failed to get contiguous memory for DMA from Xen!\n"\
184            "You either: don't have the permissions, do not have"\
185            " enough free memory under 4GB, or the hypervisor memory"\
186            "is too fragmented!";
187        goto error;
188    }
189    start_dma_addr = xen_virt_to_bus(xen_io_tlb_start);
190    swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose);
191
192    return;
193error:
194    if (repeat--) {
195        xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */
196                    (xen_io_tlb_nslabs >> 1));
197        printk(KERN_INFO "Xen-SWIOTLB: Lowering to %luMB\n",
198              (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20);
199        goto retry;
200    }
201    xen_raw_printk("%s (rc:%d)", m, rc);
202    panic("%s (rc:%d)", m, rc);
203}
204
205void *
206xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
207               dma_addr_t *dma_handle, gfp_t flags,
208               struct dma_attrs *attrs)
209{
210    void *ret;
211    int order = get_order(size);
212    u64 dma_mask = DMA_BIT_MASK(32);
213    unsigned long vstart;
214    phys_addr_t phys;
215    dma_addr_t dev_addr;
216
217    /*
218    * Ignore region specifiers - the kernel's ideas of
219    * pseudo-phys memory layout has nothing to do with the
220    * machine physical layout. We can't allocate highmem
221    * because we can't return a pointer to it.
222    */
223    flags &= ~(__GFP_DMA | __GFP_HIGHMEM);
224
225    if (dma_alloc_from_coherent(hwdev, size, dma_handle, &ret))
226        return ret;
227
228    vstart = __get_free_pages(flags, order);
229    ret = (void *)vstart;
230
231    if (!ret)
232        return ret;
233
234    if (hwdev && hwdev->coherent_dma_mask)
235        dma_mask = dma_alloc_coherent_mask(hwdev, flags);
236
237    phys = virt_to_phys(ret);
238    dev_addr = xen_phys_to_bus(phys);
239    if (((dev_addr + size - 1 <= dma_mask)) &&
240        !range_straddles_page_boundary(phys, size))
241        *dma_handle = dev_addr;
242    else {
243        if (xen_create_contiguous_region(vstart, order,
244                         fls64(dma_mask)) != 0) {
245            free_pages(vstart, order);
246            return NULL;
247        }
248        *dma_handle = virt_to_machine(ret).maddr;
249    }
250    memset(ret, 0, size);
251    return ret;
252}
253EXPORT_SYMBOL_GPL(xen_swiotlb_alloc_coherent);
254
255void
256xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
257              dma_addr_t dev_addr, struct dma_attrs *attrs)
258{
259    int order = get_order(size);
260    phys_addr_t phys;
261    u64 dma_mask = DMA_BIT_MASK(32);
262
263    if (dma_release_from_coherent(hwdev, order, vaddr))
264        return;
265
266    if (hwdev && hwdev->coherent_dma_mask)
267        dma_mask = hwdev->coherent_dma_mask;
268
269    phys = virt_to_phys(vaddr);
270
271    if (((dev_addr + size - 1 > dma_mask)) ||
272        range_straddles_page_boundary(phys, size))
273        xen_destroy_contiguous_region((unsigned long)vaddr, order);
274
275    free_pages((unsigned long)vaddr, order);
276}
277EXPORT_SYMBOL_GPL(xen_swiotlb_free_coherent);
278
279
280/*
281 * Map a single buffer of the indicated size for DMA in streaming mode. The
282 * physical address to use is returned.
283 *
284 * Once the device is given the dma address, the device owns this memory until
285 * either xen_swiotlb_unmap_page or xen_swiotlb_dma_sync_single is performed.
286 */
287dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
288                unsigned long offset, size_t size,
289                enum dma_data_direction dir,
290                struct dma_attrs *attrs)
291{
292    phys_addr_t phys = page_to_phys(page) + offset;
293    dma_addr_t dev_addr = xen_phys_to_bus(phys);
294    void *map;
295
296    BUG_ON(dir == DMA_NONE);
297    /*
298     * If the address happens to be in the device's DMA window,
299     * we can safely return the device addr and not worry about bounce
300     * buffering it.
301     */
302    if (dma_capable(dev, dev_addr, size) &&
303        !range_straddles_page_boundary(phys, size) && !swiotlb_force)
304        return dev_addr;
305
306    /*
307     * Oh well, have to allocate and map a bounce buffer.
308     */
309    map = swiotlb_tbl_map_single(dev, start_dma_addr, phys, size, dir);
310    if (!map)
311        return DMA_ERROR_CODE;
312
313    dev_addr = xen_virt_to_bus(map);
314
315    /*
316     * Ensure that the address returned is DMA'ble
317     */
318    if (!dma_capable(dev, dev_addr, size)) {
319        swiotlb_tbl_unmap_single(dev, map, size, dir);
320        dev_addr = 0;
321    }
322    return dev_addr;
323}
324EXPORT_SYMBOL_GPL(xen_swiotlb_map_page);
325
326/*
327 * Unmap a single streaming mode DMA translation. The dma_addr and size must
328 * match what was provided for in a previous xen_swiotlb_map_page call. All
329 * other usages are undefined.
330 *
331 * After this call, reads by the cpu to the buffer are guaranteed to see
332 * whatever the device wrote there.
333 */
334static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
335                 size_t size, enum dma_data_direction dir)
336{
337    phys_addr_t paddr = xen_bus_to_phys(dev_addr);
338
339    BUG_ON(dir == DMA_NONE);
340
341    /* NOTE: We use dev_addr here, not paddr! */
342    if (is_xen_swiotlb_buffer(dev_addr)) {
343        swiotlb_tbl_unmap_single(hwdev, phys_to_virt(paddr), size, dir);
344        return;
345    }
346
347    if (dir != DMA_FROM_DEVICE)
348        return;
349
350    /*
351     * phys_to_virt doesn't work with hihgmem page but we could
352     * call dma_mark_clean() with hihgmem page here. However, we
353     * are fine since dma_mark_clean() is null on POWERPC. We can
354     * make dma_mark_clean() take a physical address if necessary.
355     */
356    dma_mark_clean(phys_to_virt(paddr), size);
357}
358
359void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
360                size_t size, enum dma_data_direction dir,
361                struct dma_attrs *attrs)
362{
363    xen_unmap_single(hwdev, dev_addr, size, dir);
364}
365EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_page);
366
367/*
368 * Make physical memory consistent for a single streaming mode DMA translation
369 * after a transfer.
370 *
371 * If you perform a xen_swiotlb_map_page() but wish to interrogate the buffer
372 * using the cpu, yet do not wish to teardown the dma mapping, you must
373 * call this function before doing so. At the next point you give the dma
374 * address back to the card, you must first perform a
375 * xen_swiotlb_dma_sync_for_device, and then the device again owns the buffer
376 */
377static void
378xen_swiotlb_sync_single(struct device *hwdev, dma_addr_t dev_addr,
379            size_t size, enum dma_data_direction dir,
380            enum dma_sync_target target)
381{
382    phys_addr_t paddr = xen_bus_to_phys(dev_addr);
383
384    BUG_ON(dir == DMA_NONE);
385
386    /* NOTE: We use dev_addr here, not paddr! */
387    if (is_xen_swiotlb_buffer(dev_addr)) {
388        swiotlb_tbl_sync_single(hwdev, phys_to_virt(paddr), size, dir,
389                       target);
390        return;
391    }
392
393    if (dir != DMA_FROM_DEVICE)
394        return;
395
396    dma_mark_clean(phys_to_virt(paddr), size);
397}
398
399void
400xen_swiotlb_sync_single_for_cpu(struct device *hwdev, dma_addr_t dev_addr,
401                size_t size, enum dma_data_direction dir)
402{
403    xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_CPU);
404}
405EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_cpu);
406
407void
408xen_swiotlb_sync_single_for_device(struct device *hwdev, dma_addr_t dev_addr,
409                   size_t size, enum dma_data_direction dir)
410{
411    xen_swiotlb_sync_single(hwdev, dev_addr, size, dir, SYNC_FOR_DEVICE);
412}
413EXPORT_SYMBOL_GPL(xen_swiotlb_sync_single_for_device);
414
415/*
416 * Map a set of buffers described by scatterlist in streaming mode for DMA.
417 * This is the scatter-gather version of the above xen_swiotlb_map_page
418 * interface. Here the scatter gather list elements are each tagged with the
419 * appropriate dma address and length. They are obtained via
420 * sg_dma_{address,length}(SG).
421 *
422 * NOTE: An implementation may be able to use a smaller number of
423 * DMA address/length pairs than there are SG table elements.
424 * (for example via virtual mapping capabilities)
425 * The routine returns the number of addr/length pairs actually
426 * used, at most nents.
427 *
428 * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
429 * same here.
430 */
431int
432xen_swiotlb_map_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
433             int nelems, enum dma_data_direction dir,
434             struct dma_attrs *attrs)
435{
436    struct scatterlist *sg;
437    int i;
438
439    BUG_ON(dir == DMA_NONE);
440
441    for_each_sg(sgl, sg, nelems, i) {
442        phys_addr_t paddr = sg_phys(sg);
443        dma_addr_t dev_addr = xen_phys_to_bus(paddr);
444
445        if (swiotlb_force ||
446            !dma_capable(hwdev, dev_addr, sg->length) ||
447            range_straddles_page_boundary(paddr, sg->length)) {
448            void *map = swiotlb_tbl_map_single(hwdev,
449                               start_dma_addr,
450                               sg_phys(sg),
451                               sg->length, dir);
452            if (!map) {
453                /* Don't panic here, we expect map_sg users
454                   to do proper error handling. */
455                xen_swiotlb_unmap_sg_attrs(hwdev, sgl, i, dir,
456                               attrs);
457                sgl[0].dma_length = 0;
458                return DMA_ERROR_CODE;
459            }
460            sg->dma_address = xen_virt_to_bus(map);
461        } else
462            sg->dma_address = dev_addr;
463        sg->dma_length = sg->length;
464    }
465    return nelems;
466}
467EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg_attrs);
468
469int
470xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
471           enum dma_data_direction dir)
472{
473    return xen_swiotlb_map_sg_attrs(hwdev, sgl, nelems, dir, NULL);
474}
475EXPORT_SYMBOL_GPL(xen_swiotlb_map_sg);
476
477/*
478 * Unmap a set of streaming mode DMA translations. Again, cpu read rules
479 * concerning calls here are the same as for swiotlb_unmap_page() above.
480 */
481void
482xen_swiotlb_unmap_sg_attrs(struct device *hwdev, struct scatterlist *sgl,
483               int nelems, enum dma_data_direction dir,
484               struct dma_attrs *attrs)
485{
486    struct scatterlist *sg;
487    int i;
488
489    BUG_ON(dir == DMA_NONE);
490
491    for_each_sg(sgl, sg, nelems, i)
492        xen_unmap_single(hwdev, sg->dma_address, sg->dma_length, dir);
493
494}
495EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg_attrs);
496
497void
498xen_swiotlb_unmap_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
499             enum dma_data_direction dir)
500{
501    return xen_swiotlb_unmap_sg_attrs(hwdev, sgl, nelems, dir, NULL);
502}
503EXPORT_SYMBOL_GPL(xen_swiotlb_unmap_sg);
504
505/*
506 * Make physical memory consistent for a set of streaming mode DMA translations
507 * after a transfer.
508 *
509 * The same as swiotlb_sync_single_* but for a scatter-gather list, same rules
510 * and usage.
511 */
512static void
513xen_swiotlb_sync_sg(struct device *hwdev, struct scatterlist *sgl,
514            int nelems, enum dma_data_direction dir,
515            enum dma_sync_target target)
516{
517    struct scatterlist *sg;
518    int i;
519
520    for_each_sg(sgl, sg, nelems, i)
521        xen_swiotlb_sync_single(hwdev, sg->dma_address,
522                    sg->dma_length, dir, target);
523}
524
525void
526xen_swiotlb_sync_sg_for_cpu(struct device *hwdev, struct scatterlist *sg,
527                int nelems, enum dma_data_direction dir)
528{
529    xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_CPU);
530}
531EXPORT_SYMBOL_GPL(xen_swiotlb_sync_sg_for_cpu);
532
533void
534xen_swiotlb_sync_sg_for_device(struct device *hwdev, struct scatterlist *sg,
535                   int nelems, enum dma_data_direction dir)
536{
537    xen_swiotlb_sync_sg(hwdev, sg, nelems, dir, SYNC_FOR_DEVICE);
538}
539EXPORT_SYMBOL_GPL(xen_swiotlb_sync_sg_for_device);
540
541int
542xen_swiotlb_dma_mapping_error(struct device *hwdev, dma_addr_t dma_addr)
543{
544    return !dma_addr;
545}
546EXPORT_SYMBOL_GPL(xen_swiotlb_dma_mapping_error);
547
548/*
549 * Return whether the given device DMA address mask can be supported
550 * properly. For example, if your device can only drive the low 24-bits
551 * during bus mastering, then you would pass 0x00ffffff as the mask to
552 * this function.
553 */
554int
555xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
556{
557    return xen_virt_to_bus(xen_io_tlb_end - 1) <= mask;
558}
559EXPORT_SYMBOL_GPL(xen_swiotlb_dma_supported);
560

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