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authorAlexander van Heukelum <heukelum@mailshack.com>2008-03-01 17:09:12 +0100
committerIngo Molnar <mingo@elte.hu>2008-04-17 17:40:51 +0200
commitdedd04be71cea3d5adb14c8f674e801911c89a2f (patch)
tree616250e345885a6f43dba0f407280d0304997ae3 /arch/x86/kernel/setup_32.c
parent823c248e7cc75b4f22da914b01f8e5433cff197e (diff)
x86: reserve end-of-conventional-memory to 1MB on 32-bit
This patch adds explicit detection of the EBDA and reservation of the rom and adapter address space 0xa0000-0x100000 to the i386 kernels. Before this patch, the EBDA size was hardcoded as 4Kb. Also, the reservation of the adapter range was done by modifying the e820 map which is now not necessary any longer, and that code is removed from copy_e820_map. The amount of conventional memory and the start of the EBDA are detected by reading the BIOS data area directly. Paravirtual environments do not provide this area, so we bail out early in that case. They will just have to set up a correct memory map to start with. Signed-off-by: Alexander van Heukelum <heukelum@fastmail.fm> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch/x86/kernel/setup_32.c')
-rw-r--r--arch/x86/kernel/setup_32.c64
1 files changed, 51 insertions, 13 deletions
diff --git a/arch/x86/kernel/setup_32.c b/arch/x86/kernel/setup_32.c
index 2b3e5d45176b..14e293edd23f 100644
--- 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