Slitaz -- iasl / acpi=ht -7

root=/dev/sda1 acpi=ht
please boot with early_ioremap_debug and report the dmesg.

/usr/src/linux-2.6.30.6-slitaz/arch/x86/mm/ioremap.c

[..]line#590 
static int __init check_early_ioremap_leak(void)
{
 int count = 0;
 int i;

 for (i = 0; i < FIX_BTMAPS_SLOTS; i++)
  if (prev_map[i])
   count++;

 if (!count)  return 0;
 WARN(1, KERN_WARNING
        "Debug warning: early ioremap leak of %d areas detected.\n",
  count);
 printk(KERN_WARNING
  "please boot with early_ioremap_debug and report the dmesg.\n");

 return 1;
}
late_initcall(check_early_ioremap_leak);
[..]


Extract From 

http://ericxiao.cublog.cn/
linux引導分析 
http://blog.chinaunix.net/u1/51562/showart_1018436.html

[.. #512]
Setup_arch()  --à  early_ioremap_init()代碼如下:

void __init early_ioremap_init(void)
{
         pmd_t *pmd;
 
         if (early_ioremap_debug)

                   printk(KERN_INFO "early_ioremap_init()\n");
 

         pmd = early_ioremap_pmd(fix_to_virt(FIX_BTMAP_BEGIN));

         /*在這裡會將FIX_BTMAP_BEGIN 段的頁面表固定使用bm_pte*/
         memset(bm_pte, 0, sizeof(bm_pte));

         pmd_populate_kernel(&init_mm, pmd, bm_pte);
 
         /*

          * The boot-ioremap range spans multiple pmds, for which
          * we are not prepared:
          */

         if (pmd != early_ioremap_pmd(fix_to_virt(FIX_BTMAP_END))) {
                   WARN_ON(1);

                   printk(KERN_WARNING "pmd %p != %p\n",

                          pmd, early_ioremap_pmd(fix_to_virt(FIX_BTMAP_END)));

                   printk(KERN_WARNING "fix_to_virt(FIX_BTMAP_BEGIN): %08lx\n",
                            fix_to_virt(FIX_BTMAP_BEGIN));

                   printk(KERN_WARNING "fix_to_virt(FIX_BTMAP_END):   %08lx\n",
                            fix_to_virt(FIX_BTMAP_END));
 

                   printk(KERN_WARNING "FIX_BTMAP_END:       %d\n", FIX_BTMAP_END);

                   printk(KERN_WARNING "FIX_BTMAP_BEGIN:     %d\n",
                          FIX_BTMAP_BEGIN);
         }
}
上面的這段代碼,使FIX_BTMAP_BEGIN為起始地址對應的一個PMD對應映射的地址區間.即固定映射到bm_pte.
細心的讀者可以發現了.從FIX_BTMAP_BEGIN開始的一個PMD映射區間對應就是永久內存映射的線性地址段.沒錯,就是它.
一般說來,永久內存映射地址段只在一個PMD範圍內.若有超出一個PMD.則打印出警告信息.
[..]