| #include <linux/kernel.h> |
| #include <linux/init.h> |
| #include <linux/memblock.h> |
| |
| #include <asm/setup.h> |
| #include <asm/bios_ebda.h> |
| |
| #define BIOS_LOWMEM_KILOBYTES 0x413 |
| |
| /* |
| * 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. |
| */ |
| void __init reserve_ebda_region(void) |
| { |
| 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. */ |
| if (paravirt_enabled()) |
| return; |
| |
| /* end of low (conventional) memory */ |
| lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); |
| lowmem <<= 10; |
| |
| /* start of EBDA area */ |
| ebda_addr = get_bios_ebda(); |
| |
| /* 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 */ |
| memblock_reserve(lowmem, 0x100000 - lowmem); |
| } |
