x86,efi: Implement efi_no_storage_paranoia parameter

Using this parameter one can disable the storage_size/2 check if
he is really sure that the UEFI does sane gc and fulfills the spec.

This parameter is useful if a devices uses more than 50% of the
storage by default.
The Intel DQSW67 desktop board is such a sucker for exmaple.

Signed-off-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

2 files changed, 19 insertions, 1 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 4609e81dbc37..d1cc3a9fa14f 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -788,6 +788,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
         edd=            [EDD]
                         Format: {"off" | "on" | "skip[mbr]"}
 
+        efi_no_storage_paranoia [EFI; X86]
+                        Using this parameter you can use more than 50% of
+                        your efi variable storage. Use this parameter only if
+                        you are really sure that your UEFI does sane gc and
+                        fulfills the spec otherwise your board may brick.
+
         eisa_irq_edge=  [PARISC,HW]
                         See header of drivers/parisc/eisa.c.
 
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index 4f364c7c6111..e4a86a677ce1 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -113,6 +113,15 @@ static int __init setup_add_efi_memmap(char *arg)
 }
 early_param("add_efi_memmap", setup_add_efi_memmap);
 
+static bool efi_no_storage_paranoia;
+
+static int __init setup_storage_paranoia(char *arg)
+{
+        efi_no_storage_paranoia = true;
+        return 0;
+}
+early_param("efi_no_storage_paranoia", setup_storage_paranoia);
+
 
 static efi_status_t virt_efi_get_time(efi_time_t *tm, efi_time_cap_t *tc)
 {
@@ -1137,7 +1146,10 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
          */
 
         if (!storage_size || size > remaining_size ||
-            (max_size && size > max_size) ||
+            (max_size && size > max_size))
+                return EFI_OUT_OF_RESOURCES;
+
+        if (!efi_no_storage_paranoia &&
             ((active_size + size + VAR_METADATA_SIZE > storage_size / 2) &&
              (remaining_size - size < storage_size / 2)))
                 return EFI_OUT_OF_RESOURCES;