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 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Dynamic DMA mapping support.
  *
  * This implementation is a fallback for platforms that do not support
  * I/O TLBs (aka DMA address translation hardware).
  * Copyright (C) 2000 Asit Mallick <Asit.K.Mallick@intel.com>
  * Copyright (C) 2000 Goutham Rao <goutham.rao@intel.com>
  * Copyright (C) 2000, 2003 Hewlett-Packard Co
  *  David Mosberger-Tang <davidm@hpl.hp.com>
  *
  * 03/05/07 davidm  Switch from PCI-DMA to generic device DMA API.
  * 00/12/13 davidm  Rename to swiotlb.c and add mark_clean() to avoid
  *          unnecessary i-cache flushing.
  * 04/07/.. ak      Better overflow handling. Assorted fixes.
  * 05/09/10 linville    Add support for syncing ranges, support syncing for
  *          DMA_BIDIRECTIONAL mappings, miscellaneous cleanup.
  * 08/12/11 beckyb  Add highmem support
  */
 
 #define pr_fmt(fmt) "software IO TLB: " fmt
 
 #include <linux/cache.h>
 #include <linux/cc_platform.h>
 #include <linux/ctype.h>
 #include <linux/debugfs.h>
 #include <linux/dma-direct.h>
 #include <linux/dma-map-ops.h>
 #include <linux/export.h>
 #include <linux/gfp.h>
 #include <linux/highmem.h>
 #include <linux/io.h>
 #include <linux/iommu-helper.h>
 #include <linux/init.h>
 #include <linux/memblock.h>
 #include <linux/mm.h>
 #include <linux/pfn.h>
 #include <linux/scatterlist.h>
 #include <linux/set_memory.h>
 #include <linux/spinlock.h>
 #include <linux/string.h>
 #include <linux/swiotlb.h>
 #include <linux/types.h>
 #ifdef CONFIG_DMA_RESTRICTED_POOL
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <linux/of_reserved_mem.h>
 #include <linux/slab.h>
 #endif
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/swiotlb.h>
 
 #define SLABS_PER_PAGE (1 << (PAGE_SHIFT - IO_TLB_SHIFT))
 
 /*
  * Minimum IO TLB size to bother booting with.  Systems with mainly
  * 64bit capable cards will only lightly use the swiotlb.  If we can't
  * allocate a contiguous 1MB, we're probably in trouble anyway.
  */
 #define IO_TLB_MIN_SLABS ((1<<20) >> IO_TLB_SHIFT)
 
 #define INVALID_PHYS_ADDR (~(phys_addr_t)0)
 
 struct io_tlb_slot {
     phys_addr_t orig_addr;
     size_t alloc_size;
     unsigned int list;
 };
 
 static bool swiotlb_force_bounce;
 static bool swiotlb_force_disable;
 
 struct io_tlb_mem io_tlb_default_mem;
 
 phys_addr_t swiotlb_unencrypted_base;
 
 static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
 static unsigned long default_nareas;
 
 /**
  * struct io_tlb_area - IO TLB memory area descriptor
  *
  * This is a single area with a single lock.
  *
  * @used:   The number of used IO TLB block.
  * @index:  The slot index to start searching in this area for next round.
  * @lock:   The lock to protect the above data structures in the map and
  *      unmap calls.
  */
 struct io_tlb_area {
     unsigned long used;
     unsigned int index;
     spinlock_t lock;
 };
 
 /*
  * Round up number of slabs to the next power of 2. The last area is going
  * be smaller than the rest if default_nslabs is not power of two.
  * The number of slot in an area should be a multiple of IO_TLB_SEGSIZE,
  * otherwise a segment may span two or more areas. It conflicts with free
  * contiguous slots tracking: free slots are treated contiguous no matter
  * whether they cross an area boundary.
  *
  * Return true if default_nslabs is rounded up.
  */
 static bool round_up_default_nslabs(void)
 {
     if (!default_nareas)
         return false;
 
     if (default_nslabs < IO_TLB_SEGSIZE * default_nareas)
         default_nslabs = IO_TLB_SEGSIZE * default_nareas;
     else if (is_power_of_2(default_nslabs))
         return false;
     default_nslabs = roundup_pow_of_two(default_nslabs);
     return true;
 }
 
 static void swiotlb_adjust_nareas(unsigned int nareas)
 {
     /* use a single area when non is specified */
     if (!nareas)
         nareas = 1;
     else if (!is_power_of_2(nareas))
         nareas = roundup_pow_of_two(nareas);
 
     default_nareas = nareas;
 
     pr_info("area num %d.\n", nareas);
     if (round_up_default_nslabs())
         pr_info("SWIOTLB bounce buffer size roundup to %luMB",
             (default_nslabs << IO_TLB_SHIFT) >> 20);
 }
 
 static int __init
 setup_io_tlb_npages(char *str)
 {
     if (isdigit(*str)) {
         /* avoid tail segment of size < IO_TLB_SEGSIZE */
         default_nslabs =
             ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
     }
     if (*str == ',')
         ++str;
     if (isdigit(*str))
         swiotlb_adjust_nareas(simple_strtoul(str, &str, 0));
     if (*str == ',')
         ++str;
     if (!strcmp(str, "force"))
         swiotlb_force_bounce = true;
     else if (!strcmp(str, "noforce"))
         swiotlb_force_disable = true;
 
     return 0;
 }
 early_param("swiotlb", setup_io_tlb_npages);
 
 unsigned int swiotlb_max_segment(void)
 {
     if (!io_tlb_default_mem.nslabs)
         return 0;
     return rounddown(io_tlb_default_mem.nslabs << IO_TLB_SHIFT, PAGE_SIZE);
 }
 EXPORT_SYMBOL_GPL(swiotlb_max_segment);
 
 unsigned long swiotlb_size_or_default(void)
 {
     return default_nslabs << IO_TLB_SHIFT;
 }
 
 void __init swiotlb_adjust_size(unsigned long size)
 {
     /*
      * If swiotlb parameter has not been specified, give a chance to
      * architectures such as those supporting memory encryption to
      * adjust/expand SWIOTLB size for their use.
      */
     if (default_nslabs != IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT)
         return;
 
     size = ALIGN(size, IO_TLB_SIZE);
     default_nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
     if (round_up_default_nslabs())
         size = default_nslabs << IO_TLB_SHIFT;
     pr_info("SWIOTLB bounce buffer size adjusted to %luMB", size >> 20);
 }
 
 void swiotlb_print_info(void)
 {
     struct io_tlb_mem *mem = &io_tlb_default_mem;
 
     if (!mem->nslabs) {
         pr_warn("No low mem\n");
         return;
     }
 
     pr_info("mapped [mem %pa-%pa] (%luMB)\n", &mem->start, &mem->end,
            (mem->nslabs << IO_TLB_SHIFT) >> 20);
 }
 
 static inline unsigned long io_tlb_offset(unsigned long val)
 {
     return val & (IO_TLB_SEGSIZE - 1);
 }
 
 static inline unsigned long nr_slots(u64 val)
 {
     return DIV_ROUND_UP(val, IO_TLB_SIZE);
 }
 
 /*
  * Remap swioltb memory in the unencrypted physical address space
  * when swiotlb_unencrypted_base is set. (e.g. for Hyper-V AMD SEV-SNP
  * Isolation VMs).
  */
 #ifdef CONFIG_HAS_IOMEM
 static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
 {
     void *vaddr = NULL;
 
     if (swiotlb_unencrypted_base) {
         phys_addr_t paddr = mem->start + swiotlb_unencrypted_base;
 
         vaddr = memremap(paddr, bytes, MEMREMAP_WB);
         if (!vaddr)
             pr_err("Failed to map the unencrypted memory %pa size %lx.\n",
                    &paddr, bytes);
     }
 
     return vaddr;
 }
 #else
 static void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
 {
     return NULL;
 }
 #endif
 
 /*
  * Early SWIOTLB allocation may be too early to allow an architecture to
  * perform the desired operations.  This function allows the architecture to
  * call SWIOTLB when the operations are possible.  It needs to be called
  * before the SWIOTLB memory is used.
  */
 void __init swiotlb_update_mem_attributes(void)
 {
     struct io_tlb_mem *mem = &io_tlb_default_mem;
     void *vaddr;
     unsigned long bytes;
 
     if (!mem->nslabs || mem->late_alloc)
         return;
     vaddr = phys_to_virt(mem->start);
     bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
     set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
 
     mem->vaddr = swiotlb_mem_remap(mem, bytes);
     if (!mem->vaddr)
         mem->vaddr = vaddr;
 }
 
 static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem, phys_addr_t start,
         unsigned long nslabs, unsigned int flags,
         bool late_alloc, unsigned int nareas)
 {
     void *vaddr = phys_to_virt(start);
     unsigned long bytes = nslabs << IO_TLB_SHIFT, i;
 
     mem->nslabs = nslabs;
     mem->start = start;
     mem->end = mem->start + bytes;
     mem->late_alloc = late_alloc;
     mem->nareas = nareas;
     mem->area_nslabs = nslabs / mem->nareas;
 
     mem->force_bounce = swiotlb_force_bounce || (flags & SWIOTLB_FORCE);
 
     for (i = 0; i < mem->nareas; i++) {
         spin_lock_init(&mem->areas[i].lock);
         mem->areas[i].index = 0;
         mem->areas[i].used = 0;
     }
 
     for (i = 0; i < mem->nslabs; i++) {
         mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
         mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
         mem->slots[i].alloc_size = 0;
     }
 
     /*
      * If swiotlb_unencrypted_base is set, the bounce buffer memory will
      * be remapped and cleared in swiotlb_update_mem_attributes.
      */
     if (swiotlb_unencrypted_base)
         return;
 
     memset(vaddr, 0, bytes);
     mem->vaddr = vaddr;
     return;
 }
 
 /*
  * Statically reserve bounce buffer space and initialize bounce buffer data
  * structures for the software IO TLB used to implement the DMA API.
  */
 void __init swiotlb_init_remap(bool addressing_limit, unsigned int flags,
         int (*remap)(void *tlb, unsigned long nslabs))
 {
     struct io_tlb_mem *mem = &io_tlb_default_mem;
     unsigned long nslabs;
     size_t alloc_size;
     size_t bytes;
     void *tlb;
 
     if (!addressing_limit && !swiotlb_force_bounce)
         return;
     if (swiotlb_force_disable)
         return;
 
     /*
      * default_nslabs maybe changed when adjust area number.
      * So allocate bounce buffer after adjusting area number.
      */
     if (!default_nareas)
         swiotlb_adjust_nareas(num_possible_cpus());
 
     nslabs = default_nslabs;
     /*
      * By default allocate the bounce buffer memory from low memory, but
      * allow to pick a location everywhere for hypervisors with guest
      * memory encryption.
      */
 retry:
     bytes = PAGE_ALIGN(nslabs << IO_TLB_SHIFT);
     if (flags & SWIOTLB_ANY)
         tlb = memblock_alloc(bytes, PAGE_SIZE);
     else
         tlb = memblock_alloc_low(bytes, PAGE_SIZE);
     if (!tlb) {
         pr_warn("%s: failed to allocate tlb structure\n", __func__);
         return;
     }
 
     if (remap && remap(tlb, nslabs) < 0) {
         memblock_free(tlb, PAGE_ALIGN(bytes));
 
         nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
         if (nslabs < IO_TLB_MIN_SLABS)
             panic("%s: Failed to remap %zu bytes\n",
                   __func__, bytes);
         goto retry;
     }
 
     alloc_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), nslabs));
     mem->slots = memblock_alloc(alloc_size, PAGE_SIZE);
     if (!mem->slots)
         panic("%s: Failed to allocate %zu bytes align=0x%lx\n",
               __func__, alloc_size, PAGE_SIZE);
 
     mem->areas = memblock_alloc(array_size(sizeof(struct io_tlb_area),
         default_nareas), SMP_CACHE_BYTES);
     if (!mem->areas)
         panic("%s: Failed to allocate mem->areas.\n", __func__);
 
     swiotlb_init_io_tlb_mem(mem, __pa(tlb), nslabs, flags, false,
                 default_nareas);
 
     if (flags & SWIOTLB_VERBOSE)
         swiotlb_print_info();
 }
 
 void __init swiotlb_init(bool addressing_limit, unsigned int flags)
 {
     swiotlb_init_remap(addressing_limit, flags, NULL);
 }
 
 /*
  * Systems with larger DMA zones (those that don't support ISA) can
  * initialize the swiotlb later using the slab allocator if needed.
  * This should be just like above, but with some error catching.
  */
 int swiotlb_init_late(size_t size, gfp_t gfp_mask,
         int (*remap)(void *tlb, unsigned long nslabs))
 {
     struct io_tlb_mem *mem = &io_tlb_default_mem;
     unsigned long nslabs = ALIGN(size >> IO_TLB_SHIFT, IO_TLB_SEGSIZE);
     unsigned char *vstart = NULL;
     unsigned int order, area_order;
     bool retried = false;
     int rc = 0;
 
     if (swiotlb_force_disable)
         return 0;
 
 retry:
     order = get_order(nslabs << IO_TLB_SHIFT);
     nslabs = SLABS_PER_PAGE << order;
 
     while ((SLABS_PER_PAGE << order) > IO_TLB_MIN_SLABS) {
         vstart = (void *)__get_free_pages(gfp_mask | __GFP_NOWARN,
                           order);
         if (vstart)
             break;
         order--;
         nslabs = SLABS_PER_PAGE << order;
         retried = true;
     }
 
     if (!vstart)
         return -ENOMEM;
 
     if (remap)
         rc = remap(vstart, nslabs);
     if (rc) {
         free_pages((unsigned long)vstart, order);
 
         nslabs = ALIGN(nslabs >> 1, IO_TLB_SEGSIZE);
         if (nslabs < IO_TLB_MIN_SLABS)
             return rc;
         retried = true;
         goto retry;
     }
 
     if (retried) {
         pr_warn("only able to allocate %ld MB\n",
             (PAGE_SIZE << order) >> 20);
     }
 
     if (!default_nareas)
         swiotlb_adjust_nareas(num_possible_cpus());
 
     area_order = get_order(array_size(sizeof(*mem->areas),
         default_nareas));
     mem->areas = (struct io_tlb_area *)
         __get_free_pages(GFP_KERNEL | __GFP_ZERO, area_order);
     if (!mem->areas)
         goto error_area;
 
     mem->slots = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO,
         get_order(array_size(sizeof(*mem->slots), nslabs)));
     if (!mem->slots)
         goto error_slots;
 
     set_memory_decrypted((unsigned long)vstart,
                  (nslabs << IO_TLB_SHIFT) >> PAGE_SHIFT);
     swiotlb_init_io_tlb_mem(mem, virt_to_phys(vstart), nslabs, 0, true,
                 default_nareas);
 
     swiotlb_print_info();
     return 0;
 
 error_slots:
     free_pages((unsigned long)mem->areas, area_order);
 error_area:
     free_pages((unsigned long)vstart, order);
     return -ENOMEM;
 }
 
 void __init swiotlb_exit(void)
 {
     struct io_tlb_mem *mem = &io_tlb_default_mem;
     unsigned long tbl_vaddr;
     size_t tbl_size, slots_size;
     unsigned int area_order;
 
     if (swiotlb_force_bounce)
         return;
 
     if (!mem->nslabs)
         return;
 
     pr_info("tearing down default memory pool\n");
     tbl_vaddr = (unsigned long)phys_to_virt(mem->start);
     tbl_size = PAGE_ALIGN(mem->end - mem->start);
     slots_size = PAGE_ALIGN(array_size(sizeof(*mem->slots), mem->nslabs));
 
     set_memory_encrypted(tbl_vaddr, tbl_size >> PAGE_SHIFT);
     if (mem->late_alloc) {
         area_order = get_order(array_size(sizeof(*mem->areas),
             mem->nareas));
         free_pages((unsigned long)mem->areas, area_order);
         free_pages(tbl_vaddr, get_order(tbl_size));
         free_pages((unsigned long)mem->slots, get_order(slots_size));
     } else {
         memblock_free_late(__pa(mem->areas),
             array_size(sizeof(*mem->areas), mem->nareas));
         memblock_free_late(mem->start, tbl_size);
         memblock_free_late(__pa(mem->slots), slots_size);
     }
 
     memset(mem, 0, sizeof(*mem));
 }
 
 /*
  * Return the offset into a iotlb slot required to keep the device happy.
  */
 static unsigned int swiotlb_align_offset(struct device *dev, u64 addr)
 {
     return addr & dma_get_min_align_mask(dev) & (IO_TLB_SIZE - 1);
 }
 
 /*
  * Bounce: copy the swiotlb buffer from or back to the original dma location
  */
 static void swiotlb_bounce(struct device *dev, phys_addr_t tlb_addr, size_t size,
                enum dma_data_direction dir)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     int index = (tlb_addr - mem->start) >> IO_TLB_SHIFT;
     phys_addr_t orig_addr = mem->slots[index].orig_addr;
     size_t alloc_size = mem->slots[index].alloc_size;
     unsigned long pfn = PFN_DOWN(orig_addr);
     unsigned char *vaddr = mem->vaddr + tlb_addr - mem->start;
     unsigned int tlb_offset, orig_addr_offset;
 
     if (orig_addr == INVALID_PHYS_ADDR)
         return;
 
     tlb_offset = tlb_addr & (IO_TLB_SIZE - 1);
     orig_addr_offset = swiotlb_align_offset(dev, orig_addr);
     if (tlb_offset < orig_addr_offset) {
         dev_WARN_ONCE(dev, 1,
             "Access before mapping start detected. orig offset %u, requested offset %u.\n",
             orig_addr_offset, tlb_offset);
         return;
     }
 
     tlb_offset -= orig_addr_offset;
     if (tlb_offset > alloc_size) {
         dev_WARN_ONCE(dev, 1,
             "Buffer overflow detected. Allocation size: %zu. Mapping size: %zu+%u.\n",
             alloc_size, size, tlb_offset);
         return;
     }
 
     orig_addr += tlb_offset;
     alloc_size -= tlb_offset;
 
     if (size > alloc_size) {
         dev_WARN_ONCE(dev, 1,
             "Buffer overflow detected. Allocation size: %zu. Mapping size: %zu.\n",
             alloc_size, size);
         size = alloc_size;
     }
 
     if (PageHighMem(pfn_to_page(pfn))) {
         /* The buffer does not have a mapping.  Map it in and copy */
         unsigned int offset = orig_addr & ~PAGE_MASK;
         char *buffer;
         unsigned int sz = 0;
         unsigned long flags;
 
         while (size) {
             sz = min_t(size_t, PAGE_SIZE - offset, size);
 
             local_irq_save(flags);
             buffer = kmap_atomic(pfn_to_page(pfn));
             if (dir == DMA_TO_DEVICE)
                 memcpy(vaddr, buffer + offset, sz);
             else
                 memcpy(buffer + offset, vaddr, sz);
             kunmap_atomic(buffer);
             local_irq_restore(flags);
 
             size -= sz;
             pfn++;
             vaddr += sz;
             offset = 0;
         }
     } else if (dir == DMA_TO_DEVICE) {
         memcpy(vaddr, phys_to_virt(orig_addr), size);
     } else {
         memcpy(phys_to_virt(orig_addr), vaddr, size);
     }
 }
 
 static inline phys_addr_t slot_addr(phys_addr_t start, phys_addr_t idx)
 {
     return start + (idx << IO_TLB_SHIFT);
 }
 
 /*
  * Carefully handle integer overflow which can occur when boundary_mask == ~0UL.
  */
 static inline unsigned long get_max_slots(unsigned long boundary_mask)
 {
     if (boundary_mask == ~0UL)
         return 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
     return nr_slots(boundary_mask + 1);
 }
 
 static unsigned int wrap_area_index(struct io_tlb_mem *mem, unsigned int index)
 {
     if (index >= mem->area_nslabs)
         return 0;
     return index;
 }
 
 /*
  * Find a suitable number of IO TLB entries size that will fit this request and
  * allocate a buffer from that IO TLB pool.
  */
 static int swiotlb_do_find_slots(struct device *dev, int area_index,
         phys_addr_t orig_addr, size_t alloc_size,
         unsigned int alloc_align_mask)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     struct io_tlb_area *area = mem->areas + area_index;
     unsigned long boundary_mask = dma_get_seg_boundary(dev);
     dma_addr_t tbl_dma_addr =
         phys_to_dma_unencrypted(dev, mem->start) & boundary_mask;
     unsigned long max_slots = get_max_slots(boundary_mask);
     unsigned int iotlb_align_mask =
         dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1);
     unsigned int nslots = nr_slots(alloc_size), stride;
     unsigned int index, wrap, count = 0, i;
     unsigned int offset = swiotlb_align_offset(dev, orig_addr);
     unsigned long flags;
     unsigned int slot_base;
     unsigned int slot_index;
 
     BUG_ON(!nslots);
     BUG_ON(area_index >= mem->nareas);
 
     /*
      * For mappings with an alignment requirement don't bother looping to
      * unaligned slots once we found an aligned one.  For allocations of
      * PAGE_SIZE or larger only look for page aligned allocations.
      */
     stride = (iotlb_align_mask >> IO_TLB_SHIFT) + 1;
     if (alloc_size >= PAGE_SIZE)
         stride = max(stride, stride << (PAGE_SHIFT - IO_TLB_SHIFT));
     stride = max(stride, (alloc_align_mask >> IO_TLB_SHIFT) + 1);
 
     spin_lock_irqsave(&area->lock, flags);
     if (unlikely(nslots > mem->area_nslabs - area->used))
         goto not_found;
 
     slot_base = area_index * mem->area_nslabs;
     index = wrap = wrap_area_index(mem, ALIGN(area->index, stride));
 
     do {
         slot_index = slot_base + index;
 
         if (orig_addr &&
             (slot_addr(tbl_dma_addr, slot_index) &
              iotlb_align_mask) != (orig_addr & iotlb_align_mask)) {
             index = wrap_area_index(mem, index + 1);
             continue;
         }
 
         /*
          * If we find a slot that indicates we have 'nslots' number of
          * contiguous buffers, we allocate the buffers from that slot
          * and mark the entries as '0' indicating unavailable.
          */
         if (!iommu_is_span_boundary(slot_index, nslots,
                         nr_slots(tbl_dma_addr),
                         max_slots)) {
             if (mem->slots[slot_index].list >= nslots)
                 goto found;
         }
         index = wrap_area_index(mem, index + stride);
     } while (index != wrap);
 
 not_found:
     spin_unlock_irqrestore(&area->lock, flags);
     return -1;
 
 found:
     for (i = slot_index; i < slot_index + nslots; i++) {
         mem->slots[i].list = 0;
         mem->slots[i].alloc_size = alloc_size - (offset +
                 ((i - slot_index) << IO_TLB_SHIFT));
     }
     for (i = slot_index - 1;
          io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 &&
          mem->slots[i].list; i--)
         mem->slots[i].list = ++count;
 
     /*
      * Update the indices to avoid searching in the next round.
      */
     if (index + nslots < mem->area_nslabs)
         area->index = index + nslots;
     else
         area->index = 0;
     area->used += nslots;
     spin_unlock_irqrestore(&area->lock, flags);
     return slot_index;
 }
 
 static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
         size_t alloc_size, unsigned int alloc_align_mask)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     int start = raw_smp_processor_id() & (mem->nareas - 1);
     int i = start, index;
 
     do {
         index = swiotlb_do_find_slots(dev, i, orig_addr, alloc_size,
                           alloc_align_mask);
         if (index >= 0)
             return index;
         if (++i >= mem->nareas)
             i = 0;
     } while (i != start);
 
     return -1;
 }
 
 static unsigned long mem_used(struct io_tlb_mem *mem)
 {
     int i;
     unsigned long used = 0;
 
     for (i = 0; i < mem->nareas; i++)
         used += mem->areas[i].used;
     return used;
 }
 
 phys_addr_t swiotlb_tbl_map_single(struct device *dev, phys_addr_t orig_addr,
         size_t mapping_size, size_t alloc_size,
         unsigned int alloc_align_mask, enum dma_data_direction dir,
         unsigned long attrs)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     unsigned int offset = swiotlb_align_offset(dev, orig_addr);
     unsigned int i;
     int index;
     phys_addr_t tlb_addr;
 
     if (!mem || !mem->nslabs)
         panic("Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer");
 
     if (cc_platform_has(CC_ATTR_MEM_ENCRYPT))
         pr_warn_once("Memory encryption is active and system is using DMA bounce buffers\n");
 
     if (mapping_size > alloc_size) {
         dev_warn_once(dev, "Invalid sizes (mapping: %zd bytes, alloc: %zd bytes)",
                   mapping_size, alloc_size);
         return (phys_addr_t)DMA_MAPPING_ERROR;
     }
 
     index = swiotlb_find_slots(dev, orig_addr,
                    alloc_size + offset, alloc_align_mask);
     if (index == -1) {
         if (!(attrs & DMA_ATTR_NO_WARN))
             dev_warn_ratelimited(dev,
     "swiotlb buffer is full (sz: %zd bytes), total %lu (slots), used %lu (slots)\n",
                  alloc_size, mem->nslabs, mem_used(mem));
         return (phys_addr_t)DMA_MAPPING_ERROR;
     }
 
     /*
      * Save away the mapping from the original address to the DMA address.
      * This is needed when we sync the memory.  Then we sync the buffer if
      * needed.
      */
     for (i = 0; i < nr_slots(alloc_size + offset); i++)
         mem->slots[index + i].orig_addr = slot_addr(orig_addr, i);
     tlb_addr = slot_addr(mem->start, index) + offset;
     /*
      * When dir == DMA_FROM_DEVICE we could omit the copy from the orig
      * to the tlb buffer, if we knew for sure the device will
      * overwrite the entire current content. But we don't. Thus
      * unconditional bounce may prevent leaking swiotlb content (i.e.
      * kernel memory) to user-space.
      */
     swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_TO_DEVICE);
     return tlb_addr;
 }
 
 static void swiotlb_release_slots(struct device *dev, phys_addr_t tlb_addr)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     unsigned long flags;
     unsigned int offset = swiotlb_align_offset(dev, tlb_addr);
     int index = (tlb_addr - offset - mem->start) >> IO_TLB_SHIFT;
     int nslots = nr_slots(mem->slots[index].alloc_size + offset);
     int aindex = index / mem->area_nslabs;
     struct io_tlb_area *area = &mem->areas[aindex];
     int count, i;
 
     /*
      * Return the buffer to the free list by setting the corresponding
      * entries to indicate the number of contiguous entries available.
      * While returning the entries to the free list, we merge the entries
      * with slots below and above the pool being returned.
      */
     BUG_ON(aindex >= mem->nareas);
 
     spin_lock_irqsave(&area->lock, flags);
     if (index + nslots < ALIGN(index + 1, IO_TLB_SEGSIZE))
         count = mem->slots[index + nslots].list;
     else
         count = 0;
 
     /*
      * Step 1: return the slots to the free list, merging the slots with
      * superceeding slots
      */
     for (i = index + nslots - 1; i >= index; i--) {
         mem->slots[i].list = ++count;
         mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
         mem->slots[i].alloc_size = 0;
     }
 
     /*
      * Step 2: merge the returned slots with the preceding slots, if
      * available (non zero)
      */
     for (i = index - 1;
          io_tlb_offset(i) != IO_TLB_SEGSIZE - 1 && mem->slots[i].list;
          i--)
         mem->slots[i].list = ++count;
     area->used -= nslots;
     spin_unlock_irqrestore(&area->lock, flags);
 }
 
 /*
  * tlb_addr is the physical address of the bounce buffer to unmap.
  */
 void swiotlb_tbl_unmap_single(struct device *dev, phys_addr_t tlb_addr,
                   size_t mapping_size, enum dma_data_direction dir,
                   unsigned long attrs)
 {
     /*
      * First, sync the memory before unmapping the entry
      */
     if (!(attrs & DMA_ATTR_SKIP_CPU_SYNC) &&
         (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL))
         swiotlb_bounce(dev, tlb_addr, mapping_size, DMA_FROM_DEVICE);
 
     swiotlb_release_slots(dev, tlb_addr);
 }
 
 void swiotlb_sync_single_for_device(struct device *dev, phys_addr_t tlb_addr,
         size_t size, enum dma_data_direction dir)
 {
     if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL)
         swiotlb_bounce(dev, tlb_addr, size, DMA_TO_DEVICE);
     else
         BUG_ON(dir != DMA_FROM_DEVICE);
 }
 
 void swiotlb_sync_single_for_cpu(struct device *dev, phys_addr_t tlb_addr,
         size_t size, enum dma_data_direction dir)
 {
     if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
         swiotlb_bounce(dev, tlb_addr, size, DMA_FROM_DEVICE);
     else
         BUG_ON(dir != DMA_TO_DEVICE);
 }
 
 /*
  * Create a swiotlb mapping for the buffer at @paddr, and in case of DMAing
  * to the device copy the data into it as well.
  */
 dma_addr_t swiotlb_map(struct device *dev, phys_addr_t paddr, size_t size,
         enum dma_data_direction dir, unsigned long attrs)
 {
     phys_addr_t swiotlb_addr;
     dma_addr_t dma_addr;
 
     trace_swiotlb_bounced(dev, phys_to_dma(dev, paddr), size);
 
     swiotlb_addr = swiotlb_tbl_map_single(dev, paddr, size, size, 0, dir,
             attrs);
     if (swiotlb_addr == (phys_addr_t)DMA_MAPPING_ERROR)
         return DMA_MAPPING_ERROR;
 
     /* Ensure that the address returned is DMA'ble */
     dma_addr = phys_to_dma_unencrypted(dev, swiotlb_addr);
     if (unlikely(!dma_capable(dev, dma_addr, size, true))) {
         swiotlb_tbl_unmap_single(dev, swiotlb_addr, size, dir,
             attrs | DMA_ATTR_SKIP_CPU_SYNC);
         dev_WARN_ONCE(dev, 1,
             "swiotlb addr %pad+%zu overflow (mask %llx, bus limit %llx).\n",
             &dma_addr, size, *dev->dma_mask, dev->bus_dma_limit);
         return DMA_MAPPING_ERROR;
     }
 
     if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
         arch_sync_dma_for_device(swiotlb_addr, size, dir);
     return dma_addr;
 }
 
 size_t swiotlb_max_mapping_size(struct device *dev)
 {
     int min_align_mask = dma_get_min_align_mask(dev);
     int min_align = 0;
 
     /*
      * swiotlb_find_slots() skips slots according to
      * min align mask. This affects max mapping size.
      * Take it into acount here.
      */
     if (min_align_mask)
         min_align = roundup(min_align_mask, IO_TLB_SIZE);
 
     return ((size_t)IO_TLB_SIZE) * IO_TLB_SEGSIZE - min_align;
 }
 
 bool is_swiotlb_active(struct device *dev)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
 
     return mem && mem->nslabs;
 }
 EXPORT_SYMBOL_GPL(is_swiotlb_active);
 
 static int io_tlb_used_get(void *data, u64 *val)
 {
     *val = mem_used(&io_tlb_default_mem);
     return 0;
 }
 DEFINE_DEBUGFS_ATTRIBUTE(fops_io_tlb_used, io_tlb_used_get, NULL, "%llu\n");
 
 static void swiotlb_create_debugfs_files(struct io_tlb_mem *mem,
                      const char *dirname)
 {
     mem->debugfs = debugfs_create_dir(dirname, io_tlb_default_mem.debugfs);
     if (!mem->nslabs)
         return;
 
     debugfs_create_ulong("io_tlb_nslabs", 0400, mem->debugfs, &mem->nslabs);
     debugfs_create_file("io_tlb_used", 0400, mem->debugfs, NULL,
             &fops_io_tlb_used);
 }
 
 static int __init __maybe_unused swiotlb_create_default_debugfs(void)
 {
     swiotlb_create_debugfs_files(&io_tlb_default_mem, "swiotlb");
     return 0;
 }
 
 #ifdef CONFIG_DEBUG_FS
 late_initcall(swiotlb_create_default_debugfs);
 #endif
 
 #ifdef CONFIG_DMA_RESTRICTED_POOL
 
 struct page *swiotlb_alloc(struct device *dev, size_t size)
 {
     struct io_tlb_mem *mem = dev->dma_io_tlb_mem;
     phys_addr_t tlb_addr;
     int index;
 
     if (!mem)
         return NULL;
 
     index = swiotlb_find_slots(dev, 0, size, 0);
     if (index == -1)
         return NULL;
 
     tlb_addr = slot_addr(mem->start, index);
 
     return pfn_to_page(PFN_DOWN(tlb_addr));
 }
 
 bool swiotlb_free(struct device *dev, struct page *page, size_t size)
 {
     phys_addr_t tlb_addr = page_to_phys(page);
 
     if (!is_swiotlb_buffer(dev, tlb_addr))
         return false;
 
     swiotlb_release_slots(dev, tlb_addr);
 
     return true;
 }
 
 static int rmem_swiotlb_device_init(struct reserved_mem *rmem,
                     struct device *dev)
 {
     struct io_tlb_mem *mem = rmem->priv;
     unsigned long nslabs = rmem->size >> IO_TLB_SHIFT;
 
     /* Set Per-device io tlb area to one */
     unsigned int nareas = 1;
 
     /*
      * Since multiple devices can share the same pool, the private data,
      * io_tlb_mem struct, will be initialized by the first device attached
      * to it.
      */
     if (!mem) {
         mem = kzalloc(sizeof(*mem), GFP_KERNEL);
         if (!mem)
             return -ENOMEM;
 
         mem->slots = kcalloc(nslabs, sizeof(*mem->slots), GFP_KERNEL);
         if (!mem->slots) {
             kfree(mem);
             return -ENOMEM;
         }
 
         mem->areas = kcalloc(nareas, sizeof(*mem->areas),
                 GFP_KERNEL);
         if (!mem->areas) {
             kfree(mem->slots);
             kfree(mem);
             return -ENOMEM;
         }
 
         set_memory_decrypted((unsigned long)phys_to_virt(rmem->base),
                      rmem->size >> PAGE_SHIFT);
         swiotlb_init_io_tlb_mem(mem, rmem->base, nslabs, SWIOTLB_FORCE,
                     false, nareas);
         mem->for_alloc = true;
 
         rmem->priv = mem;
 
         swiotlb_create_debugfs_files(mem, rmem->name);
     }
 
     dev->dma_io_tlb_mem = mem;
 
     return 0;
 }
 
 static void rmem_swiotlb_device_release(struct reserved_mem *rmem,
                     struct device *dev)
 {
     dev->dma_io_tlb_mem = &io_tlb_default_mem;
 }
 
 static const struct reserved_mem_ops rmem_swiotlb_ops = {
     .device_init = rmem_swiotlb_device_init,
     .device_release = rmem_swiotlb_device_release,
 };
 
 static int __init rmem_swiotlb_setup(struct reserved_mem *rmem)
 {
     unsigned long node = rmem->fdt_node;
 
     if (of_get_flat_dt_prop(node, "reusable", NULL) ||
         of_get_flat_dt_prop(node, "linux,cma-default", NULL) ||
         of_get_flat_dt_prop(node, "linux,dma-default", NULL) ||
         of_get_flat_dt_prop(node, "no-map", NULL))
         return -EINVAL;
 
     if (PageHighMem(pfn_to_page(PHYS_PFN(rmem->base)))) {
         pr_err("Restricted DMA pool must be accessible within the linear mapping.");
         return -EINVAL;
     }
 
     rmem->ops = &rmem_swiotlb_ops;
     pr_info("Reserved memory: created restricted DMA pool at %pa, size %ld MiB\n",
         &rmem->base, (unsigned long)rmem->size / SZ_1M);
     return 0;
 }
 
 RESERVEDMEM_OF_DECLARE(dma, "restricted-dma-pool", rmem_swiotlb_setup);
 #endif /* CONFIG_DMA_RESTRICTED_POOL */

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