arch/x86/kernel/resource.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/ioport.h>
   3 #include <linux/printk.h>
   4 #include <asm/e820/api.h>
   5 #include <asm/pci_x86.h>
   6
   7 static void resource_clip(struct resource *res, resource_size_t start,
   8                           resource_size_t end)
   9 {
  10         resource_size_t low = 0, high = 0;
  11
  12         if (res->end < start || res->start > end)
  13                 return;         /* no conflict */
  14
  15         if (res->start < start)
  16                 low = start - res->start;
  17
  18         if (res->end > end)
  19                 high = res->end - end;
  20
  21         /* Keep the area above or below the conflict, whichever is larger */
  22         if (low > high)
  23                 res->end = start - 1;
  24         else
  25                 res->start = end + 1;
  26 }
  27
  28 static void remove_e820_regions(struct resource *avail)
  29 {
  30         int i;
  31         struct e820_entry *entry;
  32         u64 e820_start, e820_end;
  33         struct resource orig = *avail;
  34
  35         if (!pci_use_e820)
  36                 return;
  37
  38         for (i = 0; i < e820_table->nr_entries; i++) {
  39                 entry = &e820_table->entries[i];
  40                 e820_start = entry->addr;
  41                 e820_end = entry->addr + entry->size - 1;
  42
  43                 resource_clip(avail, e820_start, e820_end);
  44                 if (orig.start != avail->start || orig.end != avail->end) {
  45                         pr_info("resource: avoiding allocation from e820 entry [mem %#010Lx-%#010Lx]\n",
  46                                 e820_start, e820_end);
  47                         if (avail->end > avail->start)
  48                                 /*
  49                                  * Use %pa instead of %pR because "avail"
  50                                  * is typically IORESOURCE_UNSET, so %pR
  51                                  * shows the size instead of addresses.
  52                                  */
  53                                 pr_info("resource: remaining [mem %pa-%pa] available\n",
  54                                         &avail->start, &avail->end);
  55                         orig = *avail;
  56                 }
  57         }
  58 }
  59
  60 void arch_remove_reservations(struct resource *avail)
  61 {
  62         /*
  63          * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
  64          * the low 1MB unconditionally, as this area is needed for some ISA
  65          * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
  66          */
  67         if (avail->flags & IORESOURCE_MEM) {
  68                 resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
  69
  70                 remove_e820_regions(avail);
  71         }
  72 }