diff options
| -rw-r--r-- | arch/x86/platform/efi/efi.c | 46 |
1 files changed, 46 insertions, 0 deletions
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c index ebc98a68c400..75bf0e56bb53 100644 --- a/arch/x86/platform/efi/efi.c +++ b/arch/x86/platform/efi/efi.c @@ -303,6 +303,50 @@ static void __init efi_clean_memmap(void) } } +/* + * Firmware can use EfiMemoryMappedIO to request that MMIO regions be + * mapped by the OS so they can be accessed by EFI runtime services, but + * should have no other significance to the OS (UEFI r2.10, sec 7.2). + * However, most bootloaders and EFI stubs convert EfiMemoryMappedIO + * regions to E820_TYPE_RESERVED entries, which prevent Linux from + * allocating space from them (see remove_e820_regions()). + * + * Some platforms use EfiMemoryMappedIO entries for PCI MMCONFIG space and + * PCI host bridge windows, which means Linux can't allocate BAR space for + * hot-added devices. + * + * Remove large EfiMemoryMappedIO regions from the E820 map to avoid this + * problem. + * + * Retain small EfiMemoryMappedIO regions because on some platforms, these + * describe non-window space that's included in host bridge _CRS. If we + * assign that space to PCI devices, they don't work. + */ +static void __init efi_remove_e820_mmio(void) +{ + efi_memory_desc_t *md; + u64 size, start, end; + int i = 0; + + for_each_efi_memory_desc(md) { + if (md->type == EFI_MEMORY_MAPPED_IO) { + size = md->num_pages << EFI_PAGE_SHIFT; + start = md->phys_addr; + end = start + size - 1; + if (size >= 256*1024) { + pr_info("Remove mem%02u: MMIO range=[0x%08llx-0x%08llx] (%lluMB) from e820 map\n", + i, start, end, size >> 20); + e820__range_remove(start, size, + E820_TYPE_RESERVED, 1); + } else { + pr_info("Not removing mem%02u: MMIO range=[0x%08llx-0x%08llx] (%lluKB) from e820 map\n", + i, start, end, size >> 10); + } + } + i++; + } +} + void __init efi_print_memmap(void) { efi_memory_desc_t *md; @@ -474,6 +518,8 @@ void __init efi_init(void) set_bit(EFI_RUNTIME_SERVICES, &efi.flags); efi_clean_memmap(); + efi_remove_e820_mmio(); + if (efi_enabled(EFI_DBG)) efi_print_memmap(); } |