diff options
Diffstat (limited to 'arch/x86/kernel/resource.c')
| -rw-r--r-- | arch/x86/kernel/resource.c | 23 |
1 files changed, 22 insertions, 1 deletions
diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c index 9b9fb7882c20..9ae64f9af956 100644 --- a/arch/x86/kernel/resource.c +++ b/arch/x86/kernel/resource.c @@ -1,4 +1,5 @@ // SPDX-License-Identifier: GPL-2.0 +#include <linux/dmi.h> #include <linux/ioport.h> #include <asm/e820/api.h> @@ -23,11 +24,31 @@ 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; + int i, year = dmi_get_bios_year(); 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]; |