drivers/firmware/efi/libstub/unaccepted_memory.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/efi.h>
   4 #include <asm/efi.h>
   5 #include "efistub.h"
   6
   7 struct efi_unaccepted_memory *unaccepted_table;
   8
   9 efi_status_t allocate_unaccepted_bitmap(__u32 nr_desc,
  10                                         struct efi_boot_memmap *map)
  11 {
  12         efi_guid_t unaccepted_table_guid = LINUX_EFI_UNACCEPTED_MEM_TABLE_GUID;
  13         u64 unaccepted_start = ULLONG_MAX, unaccepted_end = 0, bitmap_size;
  14         efi_status_t status;
  15         int i;
  16
  17         /* Check if the table is already installed */
  18         unaccepted_table = get_efi_config_table(unaccepted_table_guid);
  19         if (unaccepted_table) {
  20                 if (unaccepted_table->version != 1) {
  21                         efi_err("Unknown version of unaccepted memory table\n");
  22                         return EFI_UNSUPPORTED;
  23                 }
  24                 return EFI_SUCCESS;
  25         }
  26
  27         /* Check if there's any unaccepted memory and find the max address */
  28         for (i = 0; i < nr_desc; i++) {
  29                 efi_memory_desc_t *d;
  30                 unsigned long m = (unsigned long)map->map;
  31
  32                 d = efi_early_memdesc_ptr(m, map->desc_size, i);
  33                 if (d->type != EFI_UNACCEPTED_MEMORY)
  34                         continue;
  35
  36                 unaccepted_start = min(unaccepted_start, d->phys_addr);
  37                 unaccepted_end = max(unaccepted_end,
  38                                      d->phys_addr + d->num_pages * PAGE_SIZE);
  39         }
  40
  41         if (unaccepted_start == ULLONG_MAX)
  42                 return EFI_SUCCESS;
  43
  44         unaccepted_start = round_down(unaccepted_start,
  45                                       EFI_UNACCEPTED_UNIT_SIZE);
  46         unaccepted_end = round_up(unaccepted_end, EFI_UNACCEPTED_UNIT_SIZE);
  47
  48         /*
  49          * If unaccepted memory is present, allocate a bitmap to track what
  50          * memory has to be accepted before access.
  51          *
  52          * One bit in the bitmap represents 2MiB in the address space:
  53          * A 4k bitmap can track 64GiB of physical address space.
  54          *
  55          * In the worst case scenario -- a huge hole in the middle of the
  56          * address space -- It needs 256MiB to handle 4PiB of the address
  57          * space.
  58          *
  59          * The bitmap will be populated in setup_e820() according to the memory
  60          * map after efi_exit_boot_services().
  61          */
  62         bitmap_size = DIV_ROUND_UP(unaccepted_end - unaccepted_start,
  63                                    EFI_UNACCEPTED_UNIT_SIZE * BITS_PER_BYTE);
  64
  65         status = efi_bs_call(allocate_pool, EFI_LOADER_DATA,
  66                              sizeof(*unaccepted_table) + bitmap_size,
  67                              (void **)&unaccepted_table);
  68         if (status != EFI_SUCCESS) {
  69                 efi_err("Failed to allocate unaccepted memory config table\n");
  70                 return status;
  71         }
  72
  73         unaccepted_table->version = 1;
  74         unaccepted_table->unit_size = EFI_UNACCEPTED_UNIT_SIZE;
  75         unaccepted_table->phys_base = unaccepted_start;
  76         unaccepted_table->size = bitmap_size;
  77         memset(unaccepted_table->bitmap, 0, bitmap_size);
  78
  79         status = efi_bs_call(install_configuration_table,
  80                              &unaccepted_table_guid, unaccepted_table);
  81         if (status != EFI_SUCCESS) {
  82                 efi_bs_call(free_pool, unaccepted_table);
  83                 efi_err("Failed to install unaccepted memory config table!\n");
  84         }
  85
  86         return status;
  87 }
  88
  89 /*
  90  * The accepted memory bitmap only works at unit_size granularity.  Take
  91  * unaligned start/end addresses and either:
  92  *  1. Accepts the memory immediately and in its entirety
  93  *  2. Accepts unaligned parts, and marks *some* aligned part unaccepted
  94  *
  95  * The function will never reach the bitmap_set() with zero bits to set.
  96  */
  97 void process_unaccepted_memory(u64 start, u64 end)
  98 {
  99         u64 unit_size = unaccepted_table->unit_size;
 100         u64 unit_mask = unaccepted_table->unit_size - 1;
 101         u64 bitmap_size = unaccepted_table->size;
 102
 103         /*
 104          * Ensure that at least one bit will be set in the bitmap by
 105          * immediately accepting all regions under 2*unit_size.  This is
 106          * imprecise and may immediately accept some areas that could
 107          * have been represented in the bitmap.  But, results in simpler
 108          * code below
 109          *
 110          * Consider case like this (assuming unit_size == 2MB):
 111          *
 112          * | 4k | 2044k |    2048k   |
 113          * ^ 0x0        ^ 2MB        ^ 4MB
 114          *
 115          * Only the first 4k has been accepted. The 0MB->2MB region can not be
 116          * represented in the bitmap. The 2MB->4MB region can be represented in
 117          * the bitmap. But, the 0MB->4MB region is <2*unit_size and will be
 118          * immediately accepted in its entirety.
 119          */
 120         if (end - start < 2 * unit_size) {
 121                 arch_accept_memory(start, end);
 122                 return;
 123         }
 124
 125         /*
 126          * No matter how the start and end are aligned, at least one unaccepted
 127          * unit_size area will remain to be marked in the bitmap.
 128          */
 129
 130         /* Immediately accept a <unit_size piece at the start: */
 131         if (start & unit_mask) {
 132                 arch_accept_memory(start, round_up(start, unit_size));
 133                 start = round_up(start, unit_size);
 134         }
 135
 136         /* Immediately accept a <unit_size piece at the end: */
 137         if (end & unit_mask) {
 138                 arch_accept_memory(round_down(end, unit_size), end);
 139                 end = round_down(end, unit_size);
 140         }
 141
 142         /*
 143          * Accept part of the range that before phys_base and cannot be recorded
 144          * into the bitmap.
 145          */
 146         if (start < unaccepted_table->phys_base) {
 147                 arch_accept_memory(start,
 148                                    min(unaccepted_table->phys_base, end));
 149                 start = unaccepted_table->phys_base;
 150         }
 151
 152         /* Nothing to record */
 153         if (end < unaccepted_table->phys_base)
 154                 return;
 155
 156         /* Translate to offsets from the beginning of the bitmap */
 157         start -= unaccepted_table->phys_base;
 158         end -= unaccepted_table->phys_base;
 159
 160         /* Accept memory that doesn't fit into bitmap */
 161         if (end > bitmap_size * unit_size * BITS_PER_BYTE) {
 162                 unsigned long phys_start, phys_end;
 163
 164                 phys_start = bitmap_size * unit_size * BITS_PER_BYTE +
 165                              unaccepted_table->phys_base;
 166                 phys_end = end + unaccepted_table->phys_base;
 167
 168                 arch_accept_memory(phys_start, phys_end);
 169                 end = bitmap_size * unit_size * BITS_PER_BYTE;
 170         }
 171
 172         /*
 173          * 'start' and 'end' are now both unit_size-aligned.
 174          * Record the range as being unaccepted:
 175          */
 176         bitmap_set(unaccepted_table->bitmap,
 177                    start / unit_size, (end - start) / unit_size);
 178 }
 179
 180 void accept_memory(phys_addr_t start, phys_addr_t end)
 181 {
 182         unsigned long range_start, range_end;
 183         unsigned long bitmap_size;
 184         u64 unit_size;
 185
 186         if (!unaccepted_table)
 187                 return;
 188
 189         unit_size = unaccepted_table->unit_size;
 190
 191         /*
 192          * Only care for the part of the range that is represented
 193          * in the bitmap.
 194          */
 195         if (start < unaccepted_table->phys_base)
 196                 start = unaccepted_table->phys_base;
 197         if (end < unaccepted_table->phys_base)
 198                 return;
 199
 200         /* Translate to offsets from the beginning of the bitmap */
 201         start -= unaccepted_table->phys_base;
 202         end -= unaccepted_table->phys_base;
 203
 204         /* Make sure not to overrun the bitmap */
 205         if (end > unaccepted_table->size * unit_size * BITS_PER_BYTE)
 206                 end = unaccepted_table->size * unit_size * BITS_PER_BYTE;
 207
 208         range_start = start / unit_size;
 209         bitmap_size = DIV_ROUND_UP(end, unit_size);
 210
 211         for_each_set_bitrange_from(range_start, range_end,
 212                                    unaccepted_table->bitmap, bitmap_size) {
 213                 unsigned long phys_start, phys_end;
 214
 215                 phys_start = range_start * unit_size + unaccepted_table->phys_base;
 216                 phys_end = range_end * unit_size + unaccepted_table->phys_base;
 217
 218                 arch_accept_memory(phys_start, phys_end);
 219                 bitmap_clear(unaccepted_table->bitmap,
 220                              range_start, range_end - range_start);
 221         }
 222 }