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
7static 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
28static 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(res: avail, start: e820_start, end: 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
60void 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(res: avail, BIOS_ROM_BASE, BIOS_ROM_END);
69
70 remove_e820_regions(avail);
71 }
72}
73