Commit 27a98fe6 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

Merge branch 'acpi-x86' 

Merge a revert of a problematic commit for 5.17-rc4.

* acpi-x86:
  x86/PCI: revert "Ignore E820 reservations for bridge windows on newer systems"
parents cb1f65c1 3eb616b2

arch/x86/kernel/resource.c

+1 −22
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

#include <linux/dmi.h>

#include <linux/ioport.h>

#include <asm/e820/api.h>
@@ -24,31 +23,11 @@ static void resource_clip(struct resource *res, resource_size_t start, 
		res->start = end + 1;

}



/*

 * Some BIOS-es contain a bug where they add addresses which map to

 * system RAM in the PCI host bridge window returned by the ACPI _CRS

 * method, see commit 4dc2287c1805 ("x86: avoid E820 regions when

 * allocating address space"). To avoid this Linux by default excludes

 * E820 reservations when allocating addresses since 2010.

 * In 2019 some systems have shown-up with E820 reservations which cover

 * the entire _CRS returned PCI host bridge window, causing all attempts

 * to assign memory to PCI BARs to fail if Linux uses E820 reservations.

 *

 * Ideally Linux would fully stop using E820 reservations, but then

 * the old systems this was added for will regress.

 * Instead keep the old behavior for old systems, while ignoring the

 * E820 reservations for any systems from now on.

 */

static void remove_e820_regions(struct resource *avail)

{

	int i, year = dmi_get_bios_year();

	int i;

	struct e820_entry *entry;



	if (year >= 2018)

		return;



	pr_info_once("PCI: Removing E820 reservations from host bridge windows\n");



	for (i = 0; i < e820_table->nr_entries; i++) {

		entry = &e820_table->entries[i];