projects / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| 0c51a965 YH |
1 | #include <linux/kernel.h> |
| 2 | #include <linux/init.h> | |
| 3 | ||
| 4 | #include <asm/setup.h> | |
| 5 | #include <asm/bios_ebda.h> | |
| 6 | ||
| 7 | #define BIOS_LOWMEM_KILOBYTES 0x413 | |
| 8 | ||
| 9 | /* | |
| 10 | * The BIOS places the EBDA/XBDA at the top of conventional | |
| 11 | * memory, and usually decreases the reported amount of | |
| 12 | * conventional memory (int 0x12) too. This also contains a | |
| 13 | * workaround for Dell systems that neglect to reserve EBDA. | |
| 14 | * The same workaround also avoids a problem with the AMD768MPX | |
| 15 | * chipset: reserve a page before VGA to prevent PCI prefetch | |
| 16 | * into it (errata #56). Usually the page is reserved anyways, | |
| 17 | * unless you have no PS/2 mouse plugged in. | |
| 18 | */ | |
| 19 | void __init reserve_ebda_region(void) | |
| 20 | { | |
| 21 | unsigned int lowmem, ebda_addr; | |
| 22 | ||
| 23 | /* To determine the position of the EBDA and the */ | |
| 24 | /* end of conventional memory, we need to look at */ | |
| 25 | /* the BIOS data area. In a paravirtual environment */ | |
| 26 | /* that area is absent. We'll just have to assume */ | |
| 27 | /* that the paravirt case can handle memory setup */ | |
| 28 | /* correctly, without our help. */ | |
| 29 | if (paravirt_enabled()) | |
| 30 | return; | |
| 31 | ||
| 32 | /* end of low (conventional) memory */ | |
| 33 | lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); | |
| 34 | lowmem <<= 10; | |
| 35 | ||
| 36 | /* start of EBDA area */ | |
| 37 | ebda_addr = get_bios_ebda(); | |
| 38 | ||
| 39 | /* Fixup: bios puts an EBDA in the top 64K segment */ | |
| 40 | /* of conventional memory, but does not adjust lowmem. */ | |
| 41 | if ((lowmem - ebda_addr) <= 0x10000) | |
| 42 | lowmem = ebda_addr; | |
| 43 | ||
| 44 | /* Fixup: bios does not report an EBDA at all. */ | |
| 45 | /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */ | |
| 46 | if ((ebda_addr == 0) && (lowmem >= 0x9f000)) | |
| 47 | lowmem = 0x9f000; | |
| 48 | ||
| 49 | /* Paranoia: should never happen, but... */ | |
| 50 | if ((lowmem == 0) || (lowmem >= 0x100000)) | |
| 51 | lowmem = 0x9f000; | |
| 52 | ||
| 53 | /* reserve all memory between lowmem and the 1MB mark */ | |
| c4ba1320 | 54 | reserve_early_overlap_ok(lowmem, 0x100000, "BIOS reserved"); |
| 0c51a965 | 55 | } |