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Commit | Line | Data |
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0c51a965 HY |
1 | #include <linux/kernel.h> |
2 | #include <linux/init.h> | |
72d7c3b3 | 3 | #include <linux/memblock.h> |
0c51a965 HY |
4 | |
5 | #include <asm/setup.h> | |
6 | #include <asm/bios_ebda.h> | |
7 | ||
8 | #define BIOS_LOWMEM_KILOBYTES 0x413 | |
9 | ||
10 | /* | |
11 | * The BIOS places the EBDA/XBDA at the top of conventional | |
12 | * memory, and usually decreases the reported amount of | |
13 | * conventional memory (int 0x12) too. This also contains a | |
14 | * workaround for Dell systems that neglect to reserve EBDA. | |
15 | * The same workaround also avoids a problem with the AMD768MPX | |
16 | * chipset: reserve a page before VGA to prevent PCI prefetch | |
17 | * into it (errata #56). Usually the page is reserved anyways, | |
18 | * unless you have no PS/2 mouse plugged in. | |
19 | */ | |
20 | void __init reserve_ebda_region(void) | |
21 | { | |
22 | unsigned int lowmem, ebda_addr; | |
23 | ||
24 | /* To determine the position of the EBDA and the */ | |
25 | /* end of conventional memory, we need to look at */ | |
26 | /* the BIOS data area. In a paravirtual environment */ | |
27 | /* that area is absent. We'll just have to assume */ | |
28 | /* that the paravirt case can handle memory setup */ | |
29 | /* correctly, without our help. */ | |
30 | if (paravirt_enabled()) | |
31 | return; | |
32 | ||
33 | /* end of low (conventional) memory */ | |
34 | lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES); | |
35 | lowmem <<= 10; | |
36 | ||
37 | /* start of EBDA area */ | |
38 | ebda_addr = get_bios_ebda(); | |
39 | ||
40 | /* Fixup: bios puts an EBDA in the top 64K segment */ | |
41 | /* of conventional memory, but does not adjust lowmem. */ | |
42 | if ((lowmem - ebda_addr) <= 0x10000) | |
43 | lowmem = ebda_addr; | |
44 | ||
45 | /* Fixup: bios does not report an EBDA at all. */ | |
46 | /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */ | |
47 | if ((ebda_addr == 0) && (lowmem >= 0x9f000)) | |
48 | lowmem = 0x9f000; | |
49 | ||
50 | /* Paranoia: should never happen, but... */ | |
51 | if ((lowmem == 0) || (lowmem >= 0x100000)) | |
52 | lowmem = 0x9f000; | |
53 | ||
54 | /* reserve all memory between lowmem and the 1MB mark */ | |
24aa0788 | 55 | memblock_reserve(lowmem, 0x100000 - lowmem); |
0c51a965 | 56 | } |