x86/kernel/resource.c

0001 // SPDX-License-Identifier: GPL-2.0
0002 #include <linux/ioport.h>
0003 #include <linux/printk.h>
0004 #include <asm/e820/api.h>
0005 #include <asm/pci_x86.h>
0006
0007 static void resource_clip(struct resource *res, resource_size_t start,
0008               resource_size_t end)
0009 {
0010     resource_size_t low = 0, high = 0;
0011
0012     if (res->end < start || res->start > end)
0013         return;     /* no conflict */
0014
0015     if (res->start < start)
0016         low = start - res->start;
0017
0018     if (res->end > end)
0019         high = res->end - end;
0020
0021     /* Keep the area above or below the conflict, whichever is larger */
0022     if (low > high)
0023         res->end = start - 1;
0024     else
0025         res->start = end + 1;
0026 }
0027
0028 static void remove_e820_regions(struct resource *avail)
0029 {
0030     int i;
0031     struct e820_entry *entry;
0032     u64 e820_start, e820_end;
0033     struct resource orig = *avail;
0034
0035     if (!pci_use_e820)
0036         return;
0037
0038     for (i = 0; i < e820_table->nr_entries; i++) {
0039         entry = &e820_table->entries[i];
0040         e820_start = entry->addr;
0041         e820_end = entry->addr + entry->size - 1;
0042
0043         resource_clip(avail, e820_start, e820_end);
0044         if (orig.start != avail->start || orig.end != avail->end) {
0045             pr_info("clipped %pR to %pR for e820 entry [mem %#010Lx-%#010Lx]\n",
0046                  &orig, avail, e820_start, e820_end);
0047             orig = *avail;
0048         }
0049     }
0050 }
0051
0052 void arch_remove_reservations(struct resource *avail)
0053 {
0054     /*
0055      * Trim out BIOS area (high 2MB) and E820 regions. We do not remove
0056      * the low 1MB unconditionally, as this area is needed for some ISA
0057      * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
0058      */
0059     if (avail->flags & IORESOURCE_MEM) {
0060         resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
0061
0062         remove_e820_regions(avail);
0063     }
0064 }