x86: reserve end-of-conventional-memory to 1MB on 32-bit

[sfrench/cifs-2.6.git] / arch / x86 / kernel / setup_32.c

diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c
index 2b3e5d45176bda99d2172a2484076e973d53cfd4..14e293edd23f5ec3f5bcfecfe4419fc8fbd48bca 100644 (file)
--- a/arch/x86/kernel/setup_32.c
+++ b/arch/x86/kernel/setup_32.c
@@ -385,15 +385,60 @@ unsigned long __init find_max_low_pfn(void)
        return max_low_pfn;
 }
 
+#define BIOS_EBDA_SEGMENT 0x40E
+#define BIOS_LOWMEM_KILOBYTES 0x413
+
 /*
- * workaround for Dell systems that neglect to reserve EBDA
+ * The BIOS places the EBDA/XBDA at the top of conventional
+ * memory, and usually decreases the reported amount of
+ * conventional memory (int 0x12) too. This also contains a
+ * workaround for Dell systems that neglect to reserve EBDA.
+ * The same workaround also avoids a problem with the AMD768MPX
+ * chipset: reserve a page before VGA to prevent PCI prefetch
+ * into it (errata #56). Usually the page is reserved anyways,
+ * unless you have no PS/2 mouse plugged in.
  */
 static void __init reserve_ebda_region(void)
 {
-       unsigned int addr;
-       addr = get_bios_ebda();
-       if (addr)
-               reserve_bootmem(addr, PAGE_SIZE, BOOTMEM_DEFAULT);
+       unsigned int lowmem, ebda_addr;
+
+       /* To determine the position of the EBDA and the */
+       /* end of conventional memory, we need to look at */
+       /* the BIOS data area. In a paravirtual environment */
+       /* that area is absent. We'll just have to assume */
+       /* that the paravirt case can handle memory setup */
+       /* correctly, without our help. */
+#ifdef CONFIG_PARAVIRT
+       if ((boot_params.hdr.version >= 0x207) &&
+                       (boot_params.hdr.hardware_subarch != 0)) {
+               return;
+       }
+#endif
+
+       /* end of low (conventional) memory */
+       lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
+       lowmem <<= 10;
+
+       /* start of EBDA area */
+       ebda_addr = *(unsigned short *)__va(BIOS_EBDA_SEGMENT);
+       ebda_addr <<= 4;
+
+       /* Fixup: bios puts an EBDA in the top 64K segment */
+       /* of conventional memory, but does not adjust lowmem. */
+       if ((lowmem - ebda_addr) <= 0x10000)
+               lowmem = ebda_addr;
+
+       /* Fixup: bios does not report an EBDA at all. */
+       /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
+       if ((ebda_addr == 0) && (lowmem >= 0x9f000))
+               lowmem = 0x9f000;
+
+       /* Paranoia: should never happen, but... */
+       if ((lowmem == 0) || (lowmem >= 0x100000))
+               lowmem = 0x9f000;
+
+       /* reserve all memory between lowmem and the 1MB mark */
+       reserve_bootmem(lowmem, 0x100000 - lowmem, BOOTMEM_DEFAULT);
 }
 
 #ifndef CONFIG_NEED_MULTIPLE_NODES
@@ -617,16 +662,9 @@ void __init setup_bootmem_allocator(void)
         */
        reserve_bootmem(0, PAGE_SIZE, BOOTMEM_DEFAULT);
 
-       /* reserve EBDA region, it's a 4K region */
+       /* reserve EBDA region */
        reserve_ebda_region();
 
-    /* could be an AMD 768MPX chipset. Reserve a page  before VGA to prevent
-       PCI prefetch into it (errata #56). Usually the page is reserved anyways,
-       unless you have no PS/2 mouse plugged in. */
-       if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
-           boot_cpu_data.x86 == 6)
-            reserve_bootmem(0xa0000 - 4096, 4096, BOOTMEM_DEFAULT);
-
 #ifdef CONFIG_SMP
        /*
         * But first pinch a few for the stack/trampoline stuff