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-rw-r--r--arch/x86/platform/efi/efi.c46
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();
}