1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/ioport.h> 3 #include <asm/e820/api.h> 4 5 static void resource_clip(struct resource *res, resource_size_t start, 6 resource_size_t end) 7 { 8 resource_size_t low = 0, high = 0; 9 10 if (res->end < start || res->start > end) 11 return; /* no conflict */ 12 13 if (res->start < start) 14 low = start - res->start; 15 16 if (res->end > end) 17 high = res->end - end; 18 19 /* Keep the area above or below the conflict, whichever is larger */ 20 if (low > high) 21 res->end = start - 1; 22 else 23 res->start = end + 1; 24 } 25 26 static void remove_e820_regions(struct resource *avail) 27 { 28 int i; 29 struct e820_entry *entry; 30 31 for (i = 0; i < e820_table->nr_entries; i++) { 32 entry = &e820_table->entries[i]; 33 34 resource_clip(avail, entry->addr, 35 entry->addr + entry->size - 1); 36 } 37 } 38 39 void arch_remove_reservations(struct resource *avail) 40 { 41 /* 42 * Trim out BIOS area (high 2MB) and E820 regions. We do not remove 43 * the low 1MB unconditionally, as this area is needed for some ISA 44 * cards requiring a memory range, e.g. the i82365 PCMCIA controller. 45 */ 46 if (avail->flags & IORESOURCE_MEM) { 47 resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END); 48 49 remove_e820_regions(avail); 50 } 51 } 52