14 files changed, 189 insertions, 89 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 867bc5bea8dc..faff6934c05a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1295,14 +1295,14 @@ config ARCH_DMA_ADDR_T_64BIT
         def_bool y
         depends on X86_64 || HIGHMEM64G
 
-config DIRECT_GBPAGES
-        bool "Enable 1GB pages for kernel pagetables" if EXPERT
-        default y
-        depends on X86_64
+config X86_DIRECT_GBPAGES
+        def_bool y
+        depends on X86_64 && !DEBUG_PAGEALLOC && !KMEMCHECK
         ---help---
-          Allow the kernel linear mapping to use 1GB pages on CPUs that
-          support it. This can improve the kernel's performance a tiny bit by
-          reducing TLB pressure. If in doubt, say "Y".
+          Certain kernel features effectively disable kernel
+          linear 1 GB mappings (even if the CPU otherwise
+          supports them), so don't confuse the user by printing
+          that we have them enabled.
 
 # Common NUMA Features
 config NUMA
diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 3563107b5060..935588d95c82 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -366,6 +366,7 @@ enum align_flags {
 struct va_alignment {
         int flags;
         unsigned long mask;
+        unsigned long bits;
 } ____cacheline_aligned;
 
 extern struct va_alignment va_align;
diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index dd9e50500297..fd470ebf924e 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -5,6 +5,7 @@
 
 #include <linux/io.h>
 #include <linux/sched.h>
+#include <linux/random.h>
 #include <asm/processor.h>
 #include <asm/apic.h>
 #include <asm/cpu.h>
@@ -488,6 +489,9 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 
                 va_align.mask     = (upperbit - 1) & PAGE_MASK;
                 va_align.flags    = ALIGN_VA_32 | ALIGN_VA_64;
+
+                /* A random value per boot for bit slice [12:upper_bit) */
+                va_align.bits = get_random_int() & va_align.mask;
         }
 }
 
diff --git a/arch/x86/kernel/devicetree.c b/arch/x86/kernel/devicetree.c
index 3d3503351242..6367a780cc8c 100644
--- a/arch/x86/kernel/devicetree.c
+++ b/arch/x86/kernel/devicetree.c
@@ -286,13 +286,13 @@ static void __init x86_flattree_get_config(void)
         initial_boot_params = dt = early_memremap(initial_dtb, map_len);
         size = of_get_flat_dt_size();
         if (map_len < size) {
-                early_iounmap(dt, map_len);
+                early_memunmap(dt, map_len);
                 initial_boot_params = dt = early_memremap(initial_dtb, size);
                 map_len = size;
         }
 
         unflatten_and_copy_device_tree();
-        early_iounmap(dt, map_len);
+        early_memunmap(dt, map_len);
 }
 #else
 static inline void x86_flattree_get_config(void) { }
diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
index 46201deee923..7d46bb260334 100644
--- a/arch/x86/kernel/e820.c
+++ b/arch/x86/kernel/e820.c
@@ -661,7 +661,7 @@ void __init parse_e820_ext(u64 phys_addr, u32 data_len)
         extmap = (struct e820entry *)(sdata->data);
         __append_e820_map(extmap, entries);
         sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
-        early_iounmap(sdata, data_len);
+        early_memunmap(sdata, data_len);
         printk(KERN_INFO "e820: extended physical RAM map:\n");
         e820_print_map("extended");
 }
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index 014466b152b5..d74ac33290ae 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -354,7 +354,7 @@ static void __init relocate_initrd(void)
                 mapaddr = ramdisk_image & PAGE_MASK;
                 p = early_memremap(mapaddr, clen+slop);
                 memcpy(q, p+slop, clen);
-                early_iounmap(p, clen+slop);
+                early_memunmap(p, clen+slop);
                 q += clen;
                 ramdisk_image += clen;
                 ramdisk_size  -= clen;
@@ -438,7 +438,7 @@ static void __init parse_setup_data(void)
                 data_len = data->len + sizeof(struct setup_data);
                 data_type = data->type;
                 pa_next = data->next;
-                early_iounmap(data, sizeof(*data));
+                early_memunmap(data, sizeof(*data));
 
                 switch (data_type) {
                 case SETUP_E820_EXT:
@@ -470,7 +470,7 @@ static void __init e820_reserve_setup_data(void)
                          E820_RAM, E820_RESERVED_KERN);
                 found = 1;
                 pa_data = data->next;
-                early_iounmap(data, sizeof(*data));
+                early_memunmap(data, sizeof(*data));
         }
         if (!found)
                 return;
@@ -491,7 +491,7 @@ static void __init memblock_x86_reserve_range_setup_data(void)
                 data = early_memremap(pa_data, sizeof(*data));
                 memblock_reserve(pa_data, sizeof(*data) + data->len);
                 pa_data = data->next;
-                early_iounmap(data, sizeof(*data));
+                early_memunmap(data, sizeof(*data));
         }
 }
 
diff --git a/arch/x86/kernel/sys_x86_64.c b/arch/x86/kernel/sys_x86_64.c
index 30277e27431a..10e0272d789a 100644
--- a/arch/x86/kernel/sys_x86_64.c
+++ b/arch/x86/kernel/sys_x86_64.c
@@ -34,10 +34,26 @@ static unsigned long get_align_mask(void)
         return va_align.mask;
 }
 
+/*
+ * To avoid aliasing in the I$ on AMD F15h, the bits defined by the
+ * va_align.bits, [12:upper_bit), are set to a random value instead of
+ * zeroing them. This random value is computed once per boot. This form
+ * of ASLR is known as "per-boot ASLR".
+ *
+ * To achieve this, the random value is added to the info.align_offset
+ * value before calling vm_unmapped_area() or ORed directly to the
+ * address.
+ */
+static unsigned long get_align_bits(void)
+{
+        return va_align.bits & get_align_mask();
+}
+
 unsigned long align_vdso_addr(unsigned long addr)
 {
         unsigned long align_mask = get_align_mask();
-        return (addr + align_mask) & ~align_mask;
+        addr = (addr + align_mask) & ~align_mask;
+        return addr | get_align_bits();
 }
 
 static int __init control_va_addr_alignment(char *str)
@@ -135,8 +151,12 @@ arch_get_unmapped_area(struct file *filp, unsigned long addr,
         info.length = len;
         info.low_limit = begin;
         info.high_limit = end;
-        info.align_mask = filp ? get_align_mask() : 0;
+        info.align_mask = 0;
         info.align_offset = pgoff << PAGE_SHIFT;
+        if (filp) {
+                info.align_mask = get_align_mask();
+                info.align_offset += get_align_bits();
+        }
         return vm_unmapped_area(&info);
 }
 
@@ -174,8 +194,12 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
         info.length = len;
         info.low_limit = PAGE_SIZE;
         info.high_limit = mm->mmap_base;
-        info.align_mask = filp ? get_align_mask() : 0;
+        info.align_mask = 0;
         info.align_offset = pgoff << PAGE_SHIFT;
+        if (filp) {
+                info.align_mask = get_align_mask();
+                info.align_offset += get_align_bits();
+        }
         addr = vm_unmapped_area(&info);
         if (!(addr & ~PAGE_MASK))
                 return addr;
diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index 52417e771af9..1d553186c434 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -29,29 +29,33 @@
 
 /*
  * Tables translating between page_cache_type_t and pte encoding.
- * Minimal supported modes are defined statically, modified if more supported
- * cache modes are available.
- * Index into __cachemode2pte_tbl is the cachemode.
- * Index into __pte2cachemode_tbl are the caching attribute bits of the pte
- * (_PAGE_PWT, _PAGE_PCD, _PAGE_PAT) at index bit positions 0, 1, 2.
+ *
+ * Minimal supported modes are defined statically, they are modified
+ * during bootup if more supported cache modes are available.
+ *
+ *   Index into __cachemode2pte_tbl[] is the cachemode.
+ *
+ *   Index into __pte2cachemode_tbl[] are the caching attribute bits of the pte
+ *   (_PAGE_PWT, _PAGE_PCD, _PAGE_PAT) at index bit positions 0, 1, 2.
  */
 uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = {
-        [_PAGE_CACHE_MODE_WB]           = 0,
-        [_PAGE_CACHE_MODE_WC]           = _PAGE_PWT,
-        [_PAGE_CACHE_MODE_UC_MINUS]     = _PAGE_PCD,
-        [_PAGE_CACHE_MODE_UC]           = _PAGE_PCD | _PAGE_PWT,
-        [_PAGE_CACHE_MODE_WT]           = _PAGE_PCD,
-        [_PAGE_CACHE_MODE_WP]           = _PAGE_PCD,
+        [_PAGE_CACHE_MODE_WB      ]     = 0         | 0        ,
+        [_PAGE_CACHE_MODE_WC      ]     = _PAGE_PWT | 0        ,
+        [_PAGE_CACHE_MODE_UC_MINUS]     = 0         | _PAGE_PCD,
+        [_PAGE_CACHE_MODE_UC      ]     = _PAGE_PWT | _PAGE_PCD,
+        [_PAGE_CACHE_MODE_WT      ]     = 0         | _PAGE_PCD,
+        [_PAGE_CACHE_MODE_WP      ]     = 0         | _PAGE_PCD,
 };
 EXPORT_SYMBOL(__cachemode2pte_tbl);
+
 uint8_t __pte2cachemode_tbl[8] = {
-        [__pte2cm_idx(0)] = _PAGE_CACHE_MODE_WB,
-        [__pte2cm_idx(_PAGE_PWT)] = _PAGE_CACHE_MODE_WC,
-        [__pte2cm_idx(_PAGE_PCD)] = _PAGE_CACHE_MODE_UC_MINUS,
-        [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD)] = _PAGE_CACHE_MODE_UC,
-        [__pte2cm_idx(_PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
-        [__pte2cm_idx(_PAGE_PWT | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
-        [__pte2cm_idx(_PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
+        [__pte2cm_idx( 0        | 0         | 0        )] = _PAGE_CACHE_MODE_WB,
+        [__pte2cm_idx(_PAGE_PWT | 0         | 0        )] = _PAGE_CACHE_MODE_WC,
+        [__pte2cm_idx( 0        | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC_MINUS,
+        [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0        )] = _PAGE_CACHE_MODE_UC,
+        [__pte2cm_idx( 0        | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB,
+        [__pte2cm_idx(_PAGE_PWT | 0         | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC,
+        [__pte2cm_idx(0         | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS,
         [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC,
 };
 EXPORT_SYMBOL(__pte2cachemode_tbl);
@@ -131,21 +135,7 @@ void  __init early_alloc_pgt_buf(void)
 
 int after_bootmem;
 
-int direct_gbpages
-#ifdef CONFIG_DIRECT_GBPAGES
-                                = 1
-#endif
-;
-
-static void __init init_gbpages(void)
-{
-#ifdef CONFIG_X86_64
-        if (direct_gbpages && cpu_has_gbpages)
-                printk(KERN_INFO "Using GB pages for direct mapping\n");
-        else
-                direct_gbpages = 0;
-#endif
-}
+early_param_on_off("gbpages", "nogbpages", direct_gbpages, CONFIG_X86_DIRECT_GBPAGES);
 
 struct map_range {
         unsigned long start;
@@ -157,16 +147,12 @@ static int page_size_mask;
 
 static void __init probe_page_size_mask(void)
 {
-        init_gbpages();
-
 #if !defined(CONFIG_DEBUG_PAGEALLOC) && !defined(CONFIG_KMEMCHECK)
         /*
          * For CONFIG_DEBUG_PAGEALLOC, identity mapping will use small pages.
          * This will simplify cpa(), which otherwise needs to support splitting
          * large pages into small in interrupt context, etc.
          */
-        if (direct_gbpages)
-                page_size_mask |= 1 << PG_LEVEL_1G;
         if (cpu_has_pse)
                 page_size_mask |= 1 << PG_LEVEL_2M;
 #endif
@@ -181,6 +167,14 @@ static void __init probe_page_size_mask(void)
                 __supported_pte_mask |= _PAGE_GLOBAL;
         } else
                 __supported_pte_mask &= ~_PAGE_GLOBAL;
+
+        /* Enable 1 GB linear kernel mappings if available: */
+        if (direct_gbpages && cpu_has_gbpages) {
+                printk(KERN_INFO "Using GB pages for direct mapping\n");
+                page_size_mask |= 1 << PG_LEVEL_1G;
+        } else {
+                direct_gbpages = 0;
+        }
 }
 
 #ifdef CONFIG_X86_32
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 30eb05ae7061..3fba623e3ba5 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -130,20 +130,6 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
         return 0;
 }
 
-static int __init parse_direct_gbpages_off(char *arg)
-{
-        direct_gbpages = 0;
-        return 0;
-}
-early_param("nogbpages", parse_direct_gbpages_off);
-
-static int __init parse_direct_gbpages_on(char *arg)
-{
-        direct_gbpages = 1;
-        return 0;
-}
-early_param("gbpages", parse_direct_gbpages_on);
-
 /*
  * NOTE: pagetable_init alloc all the fixmap pagetables contiguous on the
  * physical space so we can cache the place of the first one and move
diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c
index 536ea2fb6e33..89af288ec674 100644
--- a/arch/x86/mm/pageattr.c
+++ b/arch/x86/mm/pageattr.c
@@ -81,11 +81,9 @@ void arch_report_meminfo(struct seq_file *m)
         seq_printf(m, "DirectMap4M:    %8lu kB\n",
                         direct_pages_count[PG_LEVEL_2M] << 12);
 #endif
-#ifdef CONFIG_X86_64
         if (direct_gbpages)
                 seq_printf(m, "DirectMap1G:    %8lu kB\n",
                         direct_pages_count[PG_LEVEL_1G] << 20);
-#endif
 }
 #else
 static inline void split_page_count(int level) { }
@@ -1654,13 +1652,11 @@ int set_memory_ro(unsigned long addr, int numpages)
 {
         return change_page_attr_clear(&addr, numpages, __pgprot(_PAGE_RW), 0);
 }
-EXPORT_SYMBOL_GPL(set_memory_ro);
 
 int set_memory_rw(unsigned long addr, int numpages)
 {
         return change_page_attr_set(&addr, numpages, __pgprot(_PAGE_RW), 0);
 }
-EXPORT_SYMBOL_GPL(set_memory_rw);
 
 int set_memory_np(unsigned long addr, int numpages)
 {
diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 7ac68698406c..35af6771a95a 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -610,7 +610,7 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 }
 
 #ifdef CONFIG_STRICT_DEVMEM
-/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM*/
+/* This check is done in drivers/char/mem.c in case of STRICT_DEVMEM */
 static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 {
         return 1;
@@ -628,8 +628,8 @@ static inline int range_is_allowed(unsigned long pfn, unsigned long size)
 
         while (cursor < to) {
                 if (!devmem_is_allowed(pfn)) {
-                        printk(KERN_INFO "Program %s tried to access /dev/mem between [mem %#010Lx-%#010Lx]\n",
-                                current->comm, from, to - 1);
+                        printk(KERN_INFO "Program %s tried to access /dev/mem between [mem %#010Lx-%#010Lx], PAT prevents it\n",
+                               current->comm, from, to - 1);
                         return 0;
                 }
                 cursor += PAGE_SIZE;
diff --git a/arch/x86/mm/pgtable.c b/arch/x86/mm/pgtable.c
index 7b22adaad4f1..5a7e5252c878 100644
--- a/arch/x86/mm/pgtable.c
+++ b/arch/x86/mm/pgtable.c
@@ -275,12 +275,87 @@ static void pgd_prepopulate_pmd(struct mm_struct *mm, pgd_t *pgd, pmd_t *pmds[])
         }
 }
 
+/*
+ * Xen paravirt assumes pgd table should be in one page. 64 bit kernel also
+ * assumes that pgd should be in one page.
+ *
+ * But kernel with PAE paging that is not running as a Xen domain
+ * only needs to allocate 32 bytes for pgd instead of one page.
+ */
+#ifdef CONFIG_X86_PAE
+
+#include <linux/slab.h>
+
+#define PGD_SIZE        (PTRS_PER_PGD * sizeof(pgd_t))
+#define PGD_ALIGN       32
+
+static struct kmem_cache *pgd_cache;
+
+static int __init pgd_cache_init(void)
+{
+        /*
+         * When PAE kernel is running as a Xen domain, it does not use
+         * shared kernel pmd. And this requires a whole page for pgd.
+         */
+        if (!SHARED_KERNEL_PMD)
+                return 0;
+
+        /*
+         * when PAE kernel is not running as a Xen domain, it uses
+         * shared kernel pmd. Shared kernel pmd does not require a whole
+         * page for pgd. We are able to just allocate a 32-byte for pgd.
+         * During boot time, we create a 32-byte slab for pgd table allocation.
+         */
+        pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_ALIGN,
+                                      SLAB_PANIC, NULL);
+        if (!pgd_cache)
+                return -ENOMEM;
+
+        return 0;
+}
+core_initcall(pgd_cache_init);
+
+static inline pgd_t *_pgd_alloc(void)
+{
+        /*
+         * If no SHARED_KERNEL_PMD, PAE kernel is running as a Xen domain.
+         * We allocate one page for pgd.
+         */
+        if (!SHARED_KERNEL_PMD)
+                return (pgd_t *)__get_free_page(PGALLOC_GFP);
+
+        /*
+         * Now PAE kernel is not running as a Xen domain. We can allocate
+         * a 32-byte slab for pgd to save memory space.
+         */
+        return kmem_cache_alloc(pgd_cache, PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+        if (!SHARED_KERNEL_PMD)
+                free_page((unsigned long)pgd);
+        else
+                kmem_cache_free(pgd_cache, pgd);
+}
+#else
+static inline pgd_t *_pgd_alloc(void)
+{
+        return (pgd_t *)__get_free_page(PGALLOC_GFP);
+}
+
+static inline void _pgd_free(pgd_t *pgd)
+{
+        free_page((unsigned long)pgd);
+}
+#endif /* CONFIG_X86_PAE */
+
 pgd_t *pgd_alloc(struct mm_struct *mm)
 {
         pgd_t *pgd;
         pmd_t *pmds[PREALLOCATED_PMDS];
 
-        pgd = (pgd_t *)__get_free_page(PGALLOC_GFP);
+        pgd = _pgd_alloc();
 
         if (pgd == NULL)
                 goto out;
@@ -310,7 +385,7 @@ pgd_t *pgd_alloc(struct mm_struct *mm)
 out_free_pmds:
         free_pmds(mm, pmds);
 out_free_pgd:
-        free_page((unsigned long)pgd);
+        _pgd_free(pgd);
 out:
         return NULL;
 }
@@ -320,7 +395,7 @@ void pgd_free(struct mm_struct *mm, pgd_t *pgd)
         pgd_mop_up_pmds(mm, pgd);
         pgd_dtor(pgd);
         paravirt_pgd_free(mm, pgd);
-        free_page((unsigned long)pgd);
+        _pgd_free(pgd);
 }
 
 /*
diff --git a/arch/x86/platform/efi/efi-bgrt.c b/arch/x86/platform/efi/efi-bgrt.c
index d143d216d52b..d7f997f7c26d 100644
--- a/arch/x86/platform/efi/efi-bgrt.c
+++ b/arch/x86/platform/efi/efi-bgrt.c
@@ -67,7 +67,7 @@ void __init efi_bgrt_init(void)
 
         image = efi_lookup_mapped_addr(bgrt_tab->image_address);
         if (!image) {
-                image = early_memremap(bgrt_tab->image_address,
+                image = early_ioremap(bgrt_tab->image_address,
                                        sizeof(bmp_header));
                 ioremapped = true;
                 if (!image) {
@@ -89,7 +89,7 @@ void __init efi_bgrt_init(void)
         }
 
         if (ioremapped) {
-                image = early_memremap(bgrt_tab->image_address,
+                image = early_ioremap(bgrt_tab->image_address,
                                        bmp_header.size);
                 if (!image) {
                         pr_err("Ignoring BGRT: failed to map image memory\n");
diff --git a/include/linux/init.h b/include/linux/init.h
index 2df8e8dd10a4..21b6d768edd7 100644
--- a/include/linux/init.h
+++ b/include/linux/init.h
@@ -253,21 +253,41 @@ struct obs_kernel_param {
  * obs_kernel_param "array" too far apart in .init.setup.
  */
 #define __setup_param(str, unique_id, fn, early)                        \
-        static const char __setup_str_##unique_id[] __initconst \
-                __aligned(1) = str; \
-        static struct obs_kernel_param __setup_##unique_id      \
-                __used __section(.init.setup)                   \
-                __attribute__((aligned((sizeof(long)))))        \
+        static const char __setup_str_##unique_id[] __initconst         \
+                __aligned(1) = str;                                     \
+        static struct obs_kernel_param __setup_##unique_id              \
+                __used __section(.init.setup)                           \
+                __attribute__((aligned((sizeof(long)))))                \
                 = { __setup_str_##unique_id, fn, early }
 
-#define __setup(str, fn)                                        \
+#define __setup(str, fn)                                                \
         __setup_param(str, fn, fn, 0)
 
-/* NOTE: fn is as per module_param, not __setup!  Emits warning if fn
- * returns non-zero. */
-#define early_param(str, fn)                                    \
+/*
+ * NOTE: fn is as per module_param, not __setup!
+ * Emits warning if fn returns non-zero.
+ */
+#define early_param(str, fn)                                            \
         __setup_param(str, fn, fn, 1)
 
+#define early_param_on_off(str_on, str_off, var, config)                \
+                                                                        \
+        int var = IS_ENABLED(config);                                   \
+                                                                        \
+        static int __init parse_##var##_on(char *arg)                   \
+        {                                                               \
+                var = 1;                                                \
+                return 0;                                               \
+        }                                                               \
+        __setup_param(str_on, parse_##var##_on, parse_##var##_on, 1);   \
+                                                                        \
+        static int __init parse_##var##_off(char *arg)                  \
+        {                                                               \
+                var = 0;                                                \
+                return 0;                                               \
+        }                                                               \
+        __setup_param(str_off, parse_##var##_off, parse_##var##_off, 1)
+
 /* Relies on boot_command_line being set */
 void __init parse_early_param(void);
 void __init parse_early_options(char *cmdline);