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      1 /*	$NetBSD: i915_mm.c,v 1.2 2021/12/18 23:45:28 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright  2014 Intel Corporation
      5  *
      6  * Permission is hereby granted, free of charge, to any person obtaining a
      7  * copy of this software and associated documentation files (the "Software"),
      8  * to deal in the Software without restriction, including without limitation
      9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
     10  * and/or sell copies of the Software, and to permit persons to whom the
     11  * Software is furnished to do so, subject to the following conditions:
     12  *
     13  * The above copyright notice and this permission notice (including the next
     14  * paragraph) shall be included in all copies or substantial portions of the
     15  * Software.
     16  *
     17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
     18  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
     19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
     20  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
     21  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
     22  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
     23  * IN THE SOFTWARE.
     24  *
     25  */
     26 
     27 #include <sys/cdefs.h>
     28 __KERNEL_RCSID(0, "$NetBSD: i915_mm.c,v 1.2 2021/12/18 23:45:28 riastradh Exp $");
     29 
     30 #include <linux/mm.h>
     31 #include <linux/io-mapping.h>
     32 
     33 #include <asm/pgtable.h>
     34 
     35 #include "i915_drv.h"
     36 
     37 struct remap_pfn {
     38 	struct mm_struct *mm;
     39 	unsigned long pfn;
     40 	pgprot_t prot;
     41 
     42 	struct sgt_iter sgt;
     43 	resource_size_t iobase;
     44 };
     45 
     46 static int remap_pfn(pte_t *pte, unsigned long addr, void *data)
     47 {
     48 	struct remap_pfn *r = data;
     49 
     50 	/* Special PTE are not associated with any struct page */
     51 	set_pte_at(r->mm, addr, pte, pte_mkspecial(pfn_pte(r->pfn, r->prot)));
     52 	r->pfn++;
     53 
     54 	return 0;
     55 }
     56 
     57 #define use_dma(io) ((io) != -1)
     58 
     59 static inline unsigned long sgt_pfn(const struct remap_pfn *r)
     60 {
     61 	if (use_dma(r->iobase))
     62 		return (r->sgt.dma + r->sgt.curr + r->iobase) >> PAGE_SHIFT;
     63 	else
     64 		return r->sgt.pfn + (r->sgt.curr >> PAGE_SHIFT);
     65 }
     66 
     67 static int remap_sg(pte_t *pte, unsigned long addr, void *data)
     68 {
     69 	struct remap_pfn *r = data;
     70 
     71 	if (GEM_WARN_ON(!r->sgt.pfn))
     72 		return -EINVAL;
     73 
     74 	/* Special PTE are not associated with any struct page */
     75 	set_pte_at(r->mm, addr, pte,
     76 		   pte_mkspecial(pfn_pte(sgt_pfn(r), r->prot)));
     77 	r->pfn++; /* track insertions in case we need to unwind later */
     78 
     79 	r->sgt.curr += PAGE_SIZE;
     80 	if (r->sgt.curr >= r->sgt.max)
     81 		r->sgt = __sgt_iter(__sg_next(r->sgt.sgp), use_dma(r->iobase));
     82 
     83 	return 0;
     84 }
     85 
     86 /**
     87  * remap_io_mapping - remap an IO mapping to userspace
     88  * @vma: user vma to map to
     89  * @addr: target user address to start at
     90  * @pfn: physical address of kernel memory
     91  * @size: size of map area
     92  * @iomap: the source io_mapping
     93  *
     94  *  Note: this is only safe if the mm semaphore is held when called.
     95  */
     96 int remap_io_mapping(struct vm_area_struct *vma,
     97 		     unsigned long addr, unsigned long pfn, unsigned long size,
     98 		     struct io_mapping *iomap)
     99 {
    100 	struct remap_pfn r;
    101 	int err;
    102 
    103 #define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
    104 	GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);
    105 
    106 	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
    107 	r.mm = vma->vm_mm;
    108 	r.pfn = pfn;
    109 	r.prot = __pgprot((pgprot_val(iomap->prot) & _PAGE_CACHE_MASK) |
    110 			  (pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK));
    111 
    112 	err = apply_to_page_range(r.mm, addr, size, remap_pfn, &r);
    113 	if (unlikely(err)) {
    114 		zap_vma_ptes(vma, addr, (r.pfn - pfn) << PAGE_SHIFT);
    115 		return err;
    116 	}
    117 
    118 	return 0;
    119 }
    120 
    121 /**
    122  * remap_io_sg - remap an IO mapping to userspace
    123  * @vma: user vma to map to
    124  * @addr: target user address to start at
    125  * @size: size of map area
    126  * @sgl: Start sg entry
    127  * @iobase: Use stored dma address offset by this address or pfn if -1
    128  *
    129  *  Note: this is only safe if the mm semaphore is held when called.
    130  */
    131 int remap_io_sg(struct vm_area_struct *vma,
    132 		unsigned long addr, unsigned long size,
    133 		struct scatterlist *sgl, resource_size_t iobase)
    134 {
    135 	struct remap_pfn r = {
    136 		.mm = vma->vm_mm,
    137 		.prot = vma->vm_page_prot,
    138 		.sgt = __sgt_iter(sgl, use_dma(iobase)),
    139 		.iobase = iobase,
    140 	};
    141 	int err;
    142 
    143 	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
    144 	GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);
    145 
    146 	if (!use_dma(iobase))
    147 		flush_cache_range(vma, addr, size);
    148 
    149 	err = apply_to_page_range(r.mm, addr, size, remap_sg, &r);
    150 	if (unlikely(err)) {
    151 		zap_vma_ptes(vma, addr, r.pfn << PAGE_SHIFT);
    152 		return err;
    153 	}
    154 
    155 	return 0;
    156 }
    157