x86/efi: Runtime services virtual mapping

We map the EFI regions needed for runtime services non-contiguously,
with preserved alignment on virtual addresses starting from -4G down
for a total max space of 64G. This way, we provide for stable runtime
services addresses across kernels so that a kexec'd kernel can still use
them.

Thus, they're mapped in a separate pagetable so that we don't pollute
the kernel namespace.

Add an efi= kernel command line parameter for passing miscellaneous
options and chicken bits from the command line.

While at it, add a chicken bit called "efi=old_map" which can be used as
a fallback to the old runtime services mapping method in case there's
some b0rkage with a particular EFI implementation (haha, it is hard to
hold up the sarcasm here...).

Also, add the UEFI RT VA space to Documentation/x86/x86_64/mm.txt.

Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

9 files changed, 300 insertions, 47 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 7a0f202d482e..ed43e92b0e7e 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -835,6 +835,12 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
         edd=            [EDD]
                         Format: {"off" | "on" | "skip[mbr]"}
 
+        efi=            [EFI]
+                        Format: { "old_map" }
+                        old_map [X86-64]: switch to the old ioremap-based EFI
+                        runtime services mapping. 32-bit still uses this one by
+                        default.
+
         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
diff --git a/Documentation/x86/x86_64/mm.txt b/Documentation/x86/x86_64/mm.txt
index 881582f75c9c..c584a51add15 100644
--- a/Documentation/x86/x86_64/mm.txt
+++ b/Documentation/x86/x86_64/mm.txt
@@ -28,4 +28,11 @@ reference.
 Current X86-64 implementations only support 40 bits of address space,
 but we support up to 46 bits. This expands into MBZ space in the page tables.
 
+->trampoline_pgd:
+
+We map EFI runtime services in the aforementioned PGD in the virtual
+range of 64Gb (arbitrarily set, can be raised if needed)
+
+0xffffffef00000000 - 0xffffffff00000000
+
 -Andi Kleen, Jul 2004
diff --git a/arch/x86/include/asm/efi.h b/arch/x86/include/asm/efi.h
index 65c6e6e3a552..89a05b0507b9 100644
--- a/arch/x86/include/asm/efi.h
+++ b/arch/x86/include/asm/efi.h
@@ -1,6 +1,24 @@
 #ifndef _ASM_X86_EFI_H
 #define _ASM_X86_EFI_H
 
+/*
+ * We map the EFI regions needed for runtime services non-contiguously,
+ * with preserved alignment on virtual addresses starting from -4G down
+ * for a total max space of 64G. This way, we provide for stable runtime
+ * services addresses across kernels so that a kexec'd kernel can still
+ * use them.
+ *
+ * This is the main reason why we're doing stable VA mappings for RT
+ * services.
+ *
+ * This flag is used in conjuction with a chicken bit called
+ * "efi=old_map" which can be used as a fallback to the old runtime
+ * services mapping method in case there's some b0rkage with a
+ * particular EFI implementation (haha, it is hard to hold up the
+ * sarcasm here...).
+ */
+#define EFI_OLD_MEMMAP          EFI_ARCH_1
+
 #ifdef CONFIG_X86_32
 
 #define EFI_LOADER_SIGNATURE    "EL32"
@@ -69,24 +87,31 @@ extern u64 efi_call6(void *fp, u64 arg1, u64 arg2, u64 arg3,
         efi_call6((f), (u64)(a1), (u64)(a2), (u64)(a3),         \
                   (u64)(a4), (u64)(a5), (u64)(a6))
 
+#define _efi_call_virtX(x, f, ...)                                      \
+({                                                                      \
+        efi_status_t __s;                                               \
+                                                                        \
+        efi_sync_low_kernel_mappings();                                 \
+        preempt_disable();                                              \
+        __s = efi_call##x((void *)efi.systab->runtime->f, __VA_ARGS__); \
+        preempt_enable();                                               \
+        __s;                                                            \
+})
+
 #define efi_call_virt0(f)                               \
-        efi_call0((efi.systab->runtime->f))
-#define efi_call_virt1(f, a1)                                   \
-        efi_call1((efi.systab->runtime->f), (u64)(a1))
-#define efi_call_virt2(f, a1, a2)                                       \
-        efi_call2((efi.systab->runtime->f), (u64)(a1), (u64)(a2))
-#define efi_call_virt3(f, a1, a2, a3)                                   \
-        efi_call3((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
-                  (u64)(a3))
-#define efi_call_virt4(f, a1, a2, a3, a4)                               \
-        efi_call4((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
-                  (u64)(a3), (u64)(a4))
-#define efi_call_virt5(f, a1, a2, a3, a4, a5)                           \
-        efi_call5((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
-                  (u64)(a3), (u64)(a4), (u64)(a5))
-#define efi_call_virt6(f, a1, a2, a3, a4, a5, a6)                       \
-        efi_call6((efi.systab->runtime->f), (u64)(a1), (u64)(a2), \
-                  (u64)(a3), (u64)(a4), (u64)(a5), (u64)(a6))
+        _efi_call_virtX(0, f)
+#define efi_call_virt1(f, a1)                           \
+        _efi_call_virtX(1, f, (u64)(a1))
+#define efi_call_virt2(f, a1, a2)                       \
+        _efi_call_virtX(2, f, (u64)(a1), (u64)(a2))
+#define efi_call_virt3(f, a1, a2, a3)                   \
+        _efi_call_virtX(3, f, (u64)(a1), (u64)(a2), (u64)(a3))
+#define efi_call_virt4(f, a1, a2, a3, a4)               \
+        _efi_call_virtX(4, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4))
+#define efi_call_virt5(f, a1, a2, a3, a4, a5)           \
+        _efi_call_virtX(5, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4), (u64)(a5))
+#define efi_call_virt6(f, a1, a2, a3, a4, a5, a6)       \
+        _efi_call_virtX(6, f, (u64)(a1), (u64)(a2), (u64)(a3), (u64)(a4), (u64)(a5), (u64)(a6))
 
 extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
                                  u32 type, u64 attribute);
@@ -95,12 +120,17 @@ extern void __iomem *efi_ioremap(unsigned long addr, unsigned long size,
 
 extern int add_efi_memmap;
 extern unsigned long x86_efi_facility;
+extern struct efi_scratch efi_scratch;
 extern void efi_set_executable(efi_memory_desc_t *md, bool executable);
 extern int efi_memblock_x86_reserve_range(void);
 extern void efi_call_phys_prelog(void);
 extern void efi_call_phys_epilog(void);
 extern void efi_unmap_memmap(void);
 extern void efi_memory_uc(u64 addr, unsigned long size);
+extern void __init efi_map_region(efi_memory_desc_t *md);
+extern void efi_sync_low_kernel_mappings(void);
+extern void efi_setup_page_tables(void);
+extern void __init old_map_region(efi_memory_desc_t *md);
 
 #ifdef CONFIG_EFI
 
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index f4843e031131..028e28b6fc2c 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -379,7 +379,8 @@ static inline void update_page_count(int level, unsigned long pages) { }
  */
 extern pte_t *lookup_address(unsigned long address, unsigned int *level);
 extern phys_addr_t slow_virt_to_phys(void *__address);
-
+extern int kernel_map_pages_in_pgd(pgd_t *pgd, u64 pfn, unsigned long address,
+                                   unsigned numpages, unsigned long page_flags);
 #endif  /* !__ASSEMBLY__ */
 
 #endif /* _ASM_X86_PGTABLE_DEFS_H */
diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index f396163b0402..b453069236fd 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -12,6 +12,8 @@
  *      Bibo Mao <bibo.mao@intel.com>
  *      Chandramouli Narayanan <mouli@linux.intel.com>
  *      Huang Ying <ying.huang@intel.com>
+ * Copyright (C) 2013 SuSE Labs
+ *      Borislav Petkov <bp@suse.de> - runtime services VA mapping
  *
  * Copied from efi_32.c to eliminate the duplicated code between EFI
  * 32/64 support code. --ying 2007-10-26
@@ -745,21 +747,56 @@ void efi_memory_uc(u64 addr, unsigned long size)
         set_memory_uc(addr, npages);
 }
 
+void __init old_map_region(efi_memory_desc_t *md)
+{
+        u64 start_pfn, end_pfn, end;
+        unsigned long size;
+        void *va;
+
+        start_pfn = PFN_DOWN(md->phys_addr);
+        size      = md->num_pages << PAGE_SHIFT;
+        end       = md->phys_addr + size;
+        end_pfn   = PFN_UP(end);
+
+        if (pfn_range_is_mapped(start_pfn, end_pfn)) {
+                va = __va(md->phys_addr);
+
+                if (!(md->attribute & EFI_MEMORY_WB))
+                        efi_memory_uc((u64)(unsigned long)va, size);
+        } else
+                va = efi_ioremap(md->phys_addr, size,
+                                 md->type, md->attribute);
+
+        md->virt_addr = (u64) (unsigned long) va;
+        if (!va)
+                pr_err("ioremap of 0x%llX failed!\n",
+                       (unsigned long long)md->phys_addr);
+}
+
 /*
  * This function will switch the EFI runtime services to virtual mode.
- * Essentially, look through the EFI memmap and map every region that
- * has the runtime attribute bit set in its memory descriptor and update
- * that memory descriptor with the virtual address obtained from ioremap().
- * This enables the runtime services to be called without having to
+ * Essentially, we look through the EFI memmap and map every region that
+ * has the runtime attribute bit set in its memory descriptor into the
+ * ->trampoline_pgd page table using a top-down VA allocation scheme.
+ *
+ * The old method which used to update that memory descriptor with the
+ * virtual address obtained from ioremap() is still supported when the
+ * kernel is booted with efi=old_map on its command line. Same old
+ * method enabled the runtime services to be called without having to
  * thunk back into physical mode for every invocation.
+ *
+ * The new method does a pagetable switch in a preemption-safe manner
+ * so that we're in a different address space when calling a runtime
+ * function. For function arguments passing we do copy the PGDs of the
+ * kernel page table into ->trampoline_pgd prior to each call.
  */
 void __init efi_enter_virtual_mode(void)
 {
         efi_memory_desc_t *md, *prev_md = NULL;
-        efi_status_t status;
+        void *p, *new_memmap = NULL;
         unsigned long size;
-        u64 end, systab, start_pfn, end_pfn;
-        void *p, *va, *new_memmap = NULL;
+        efi_status_t status;
+        u64 end, systab;
         int count = 0;
 
         efi.systab = NULL;
@@ -768,7 +805,6 @@ void __init efi_enter_virtual_mode(void)
          * We don't do virtual mode, since we don't do runtime services, on
          * non-native EFI
          */
-
         if (!efi_is_native()) {
                 efi_unmap_memmap();
                 return;
@@ -799,6 +835,7 @@ void __init efi_enter_virtual_mode(void)
                         continue;
                 }
                 prev_md = md;
+
         }
 
         for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
@@ -808,33 +845,18 @@ void __init efi_enter_virtual_mode(void)
                     md->type != EFI_BOOT_SERVICES_DATA)
                         continue;
 
+                efi_map_region(md);
+
                 size = md->num_pages << EFI_PAGE_SHIFT;
                 end = md->phys_addr + size;
 
-                start_pfn = PFN_DOWN(md->phys_addr);
-                end_pfn = PFN_UP(end);
-                if (pfn_range_is_mapped(start_pfn, end_pfn)) {
-                        va = __va(md->phys_addr);
-
-                        if (!(md->attribute & EFI_MEMORY_WB))
-                                efi_memory_uc((u64)(unsigned long)va, size);
-                } else
-                        va = efi_ioremap(md->phys_addr, size,
-                                         md->type, md->attribute);
-
-                md->virt_addr = (u64) (unsigned long) va;
-
-                if (!va) {
-                        pr_err("ioremap of 0x%llX failed!\n",
-                               (unsigned long long)md->phys_addr);
-                        continue;
-                }
-
                 systab = (u64) (unsigned long) efi_phys.systab;
                 if (md->phys_addr <= systab && systab < end) {
                         systab += md->virt_addr - md->phys_addr;
+
                         efi.systab = (efi_system_table_t *) (unsigned long) systab;
                 }
+
                 new_memmap = krealloc(new_memmap,
                                       (count + 1) * memmap.desc_size,
                                       GFP_KERNEL);
@@ -845,6 +867,9 @@ void __init efi_enter_virtual_mode(void)
 
         BUG_ON(!efi.systab);
 
+        efi_setup_page_tables();
+        efi_sync_low_kernel_mappings();
+
         status = phys_efi_set_virtual_address_map(
                 memmap.desc_size * count,
                 memmap.desc_size,
@@ -877,7 +902,8 @@ void __init efi_enter_virtual_mode(void)
         efi.query_variable_info = virt_efi_query_variable_info;
         efi.update_capsule = virt_efi_update_capsule;
         efi.query_capsule_caps = virt_efi_query_capsule_caps;
-        if (__supported_pte_mask & _PAGE_NX)
+
+        if (efi_enabled(EFI_OLD_MEMMAP) && (__supported_pte_mask & _PAGE_NX))
                 runtime_code_page_mkexec();
 
         kfree(new_memmap);
@@ -1007,3 +1033,15 @@ efi_status_t efi_query_variable_store(u32 attributes, unsigned long size)
         return EFI_SUCCESS;
 }
 EXPORT_SYMBOL_GPL(efi_query_variable_store);
+
+static int __init parse_efi_cmdline(char *str)
+{
+        if (*str == '=')
+                str++;
+
+        if (!strncmp(str, "old_map", 7))
+                set_bit(EFI_OLD_MEMMAP, &x86_efi_facility);
+
+        return 0;
+}
+early_param("efi", parse_efi_cmdline);
diff --git a/arch/x86/platform/efi/efi_32.c b/arch/x86/platform/efi/efi_32.c
index 40e446941dd7..e94557cf5487 100644
--- a/arch/x86/platform/efi/efi_32.c
+++ b/arch/x86/platform/efi/efi_32.c
@@ -37,9 +37,16 @@
  * claim EFI runtime service handler exclusively and to duplicate a memory in
  * low memory space say 0 - 3G.
  */
-
 static unsigned long efi_rt_eflags;
 
+void efi_sync_low_kernel_mappings(void) {}
+void efi_setup_page_tables(void) {}
+
+void __init efi_map_region(efi_memory_desc_t *md)
+{
+        old_map_region(md);
+}
+
 void efi_call_phys_prelog(void)
 {
         struct desc_ptr gdt_descr;
diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 39a0e7f1f0a3..bf286c386d33 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -38,10 +38,28 @@
 #include <asm/efi.h>
 #include <asm/cacheflush.h>
 #include <asm/fixmap.h>
+#include <asm/realmode.h>
 
 static pgd_t *save_pgd __initdata;
 static unsigned long efi_flags __initdata;
 
+/*
+ * We allocate runtime services regions bottom-up, starting from -4G, i.e.
+ * 0xffff_ffff_0000_0000 and limit EFI VA mapping space to 64G.
+ */
+static u64 efi_va       = -4 * (1UL << 30);
+#define EFI_VA_END      (-68 * (1UL << 30))
+
+/*
+ * Scratch space used for switching the pagetable in the EFI stub
+ */
+struct efi_scratch {
+        u64 r15;
+        u64 prev_cr3;
+        pgd_t *efi_pgt;
+        bool use_pgd;
+};
+
 static void __init early_code_mapping_set_exec(int executable)
 {
         efi_memory_desc_t *md;
@@ -65,6 +83,9 @@ void __init efi_call_phys_prelog(void)
         int pgd;
         int n_pgds;
 
+        if (!efi_enabled(EFI_OLD_MEMMAP))
+                return;
+
         early_code_mapping_set_exec(1);
         local_irq_save(efi_flags);
 
@@ -86,6 +107,10 @@ void __init efi_call_phys_epilog(void)
          */
         int pgd;
         int n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);
+
+        if (!efi_enabled(EFI_OLD_MEMMAP))
+                return;
+
         for (pgd = 0; pgd < n_pgds; pgd++)
                 set_pgd(pgd_offset_k(pgd * PGDIR_SIZE), save_pgd[pgd]);
         kfree(save_pgd);
@@ -94,6 +119,90 @@ void __init efi_call_phys_epilog(void)
         early_code_mapping_set_exec(0);
 }
 
+/*
+ * Add low kernel mappings for passing arguments to EFI functions.
+ */
+void efi_sync_low_kernel_mappings(void)
+{
+        unsigned num_pgds;
+        pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+
+        if (efi_enabled(EFI_OLD_MEMMAP))
+                return;
+
+        num_pgds = pgd_index(MODULES_END - 1) - pgd_index(PAGE_OFFSET);
+
+        memcpy(pgd + pgd_index(PAGE_OFFSET),
+                init_mm.pgd + pgd_index(PAGE_OFFSET),
+                sizeof(pgd_t) * num_pgds);
+}
+
+void efi_setup_page_tables(void)
+{
+        efi_scratch.efi_pgt = (pgd_t *)(unsigned long)real_mode_header->trampoline_pgd;
+
+        if (!efi_enabled(EFI_OLD_MEMMAP))
+                efi_scratch.use_pgd = true;
+}
+
+static void __init __map_region(efi_memory_desc_t *md, u64 va)
+{
+        pgd_t *pgd = (pgd_t *)__va(real_mode_header->trampoline_pgd);
+        unsigned long pf = 0, size;
+        u64 end;
+
+        if (!(md->attribute & EFI_MEMORY_WB))
+                pf |= _PAGE_PCD;
+
+        size = md->num_pages << PAGE_SHIFT;
+        end  = va + size;
+
+        if (kernel_map_pages_in_pgd(pgd, md->phys_addr, va, md->num_pages, pf))
+                pr_warn("Error mapping PA 0x%llx -> VA 0x%llx!\n",
+                           md->phys_addr, va);
+}
+
+void __init efi_map_region(efi_memory_desc_t *md)
+{
+        unsigned long size = md->num_pages << PAGE_SHIFT;
+        u64 pa = md->phys_addr;
+
+        if (efi_enabled(EFI_OLD_MEMMAP))
+                return old_map_region(md);
+
+        /*
+         * Make sure the 1:1 mappings are present as a catch-all for b0rked
+         * firmware which doesn't update all internal pointers after switching
+         * to virtual mode and would otherwise crap on us.
+         */
+        __map_region(md, md->phys_addr);
+
+        efi_va -= size;
+
+        /* Is PA 2M-aligned? */
+        if (!(pa & (PMD_SIZE - 1))) {
+                efi_va &= PMD_MASK;
+        } else {
+                u64 pa_offset = pa & (PMD_SIZE - 1);
+                u64 prev_va = efi_va;
+
+                /* get us the same offset within this 2M page */
+                efi_va = (efi_va & PMD_MASK) + pa_offset;
+
+                if (efi_va > prev_va)
+                        efi_va -= PMD_SIZE;
+        }
+
+        if (efi_va < EFI_VA_END) {
+                pr_warn(FW_WARN "VA address range overflow!\n");
+                return;
+        }
+
+        /* Do the VA map */
+        __map_region(md, efi_va);
+        md->virt_addr = efi_va;
+}
+
 void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
                                  u32 type, u64 attribute)
 {
diff --git a/arch/x86/platform/efi/efi_stub_64.S b/arch/x86/platform/efi/efi_stub_64.S
index 4c07ccab8146..88073b140298 100644
--- a/arch/x86/platform/efi/efi_stub_64.S
+++ b/arch/x86/platform/efi/efi_stub_64.S
@@ -34,10 +34,47 @@
         mov %rsi, %cr0;                 \
         mov (%rsp), %rsp
 
+        /* stolen from gcc */
+        .macro FLUSH_TLB_ALL
+        movq %r15, efi_scratch(%rip)
+        movq %r14, efi_scratch+8(%rip)
+        movq %cr4, %r15
+        movq %r15, %r14
+        andb $0x7f, %r14b
+        movq %r14, %cr4
+        movq %r15, %cr4
+        movq efi_scratch+8(%rip), %r14
+        movq efi_scratch(%rip), %r15
+        .endm
+
+        .macro SWITCH_PGT
+        cmpb $0, efi_scratch+24(%rip)
+        je 1f
+        movq %r15, efi_scratch(%rip)            # r15
+        # save previous CR3
+        movq %cr3, %r15
+        movq %r15, efi_scratch+8(%rip)          # prev_cr3
+        movq efi_scratch+16(%rip), %r15         # EFI pgt
+        movq %r15, %cr3
+        1:
+        .endm
+
+        .macro RESTORE_PGT
+        cmpb $0, efi_scratch+24(%rip)
+        je 2f
+        movq efi_scratch+8(%rip), %r15
+        movq %r15, %cr3
+        movq efi_scratch(%rip), %r15
+        FLUSH_TLB_ALL
+        2:
+        .endm
+
 ENTRY(efi_call0)
         SAVE_XMM
         subq $32, %rsp
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $32, %rsp
         RESTORE_XMM
         ret
@@ -47,7 +84,9 @@ ENTRY(efi_call1)
         SAVE_XMM
         subq $32, %rsp
         mov  %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $32, %rsp
         RESTORE_XMM
         ret
@@ -57,7 +96,9 @@ ENTRY(efi_call2)
         SAVE_XMM
         subq $32, %rsp
         mov  %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $32, %rsp
         RESTORE_XMM
         ret
@@ -68,7 +109,9 @@ ENTRY(efi_call3)
         subq $32, %rsp
         mov  %rcx, %r8
         mov  %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $32, %rsp
         RESTORE_XMM
         ret
@@ -80,7 +123,9 @@ ENTRY(efi_call4)
         mov %r8, %r9
         mov %rcx, %r8
         mov %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $32, %rsp
         RESTORE_XMM
         ret
@@ -93,7 +138,9 @@ ENTRY(efi_call5)
         mov %r8, %r9
         mov %rcx, %r8
         mov %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $48, %rsp
         RESTORE_XMM
         ret
@@ -109,8 +156,15 @@ ENTRY(efi_call6)
         mov %r8, %r9
         mov %rcx, %r8
         mov %rsi, %rcx
+        SWITCH_PGT
         call *%rdi
+        RESTORE_PGT
         addq $48, %rsp
         RESTORE_XMM
         ret
 ENDPROC(efi_call6)
+
+        .data
+ENTRY(efi_scratch)
+        .fill 3,8,0
+        .byte 0
diff --git a/include/linux/efi.h b/include/linux/efi.h
index bc5687d0f315..6c0ca528300c 100644
--- a/include/linux/efi.h
+++ b/include/linux/efi.h
@@ -653,6 +653,7 @@ extern int __init efi_setup_pcdp_console(char *);
 #define EFI_RUNTIME_SERVICES    3       /* Can we use runtime services? */
 #define EFI_MEMMAP              4       /* Can we use EFI memory map? */
 #define EFI_64BIT               5       /* Is the firmware 64-bit? */
+#define EFI_ARCH_1              6       /* First arch-specific bit */
 
 #ifdef CONFIG_EFI
 # ifdef CONFIG_X86