1#include <linux/kernel.h>
 2#include <linux/init.h>
 3#include <linux/memblock.h>
 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 */
 
 
 
 
 
20void __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 */
55	memblock_reserve(lowmem, 0x100000 - lowmem);
56}

 1#include <linux/kernel.h>
 2#include <linux/init.h>
 3#include <linux/memblock.h>
 4
 5#include <asm/setup.h>
 6#include <asm/bios_ebda.h>
 7
 
 
 8/*
 9 * The BIOS places the EBDA/XBDA at the top of conventional
10 * memory, and usually decreases the reported amount of
11 * conventional memory (int 0x12) too. This also contains a
12 * workaround for Dell systems that neglect to reserve EBDA.
13 * The same workaround also avoids a problem with the AMD768MPX
14 * chipset: reserve a page before VGA to prevent PCI prefetch
15 * into it (errata #56). Usually the page is reserved anyways,
16 * unless you have no PS/2 mouse plugged in.
17 *
18 * This functions is deliberately very conservative.  Losing
19 * memory in the bottom megabyte is rarely a problem, as long
20 * as we have enough memory to install the trampoline.  Using
21 * memory that is in use by the BIOS or by some DMA device
22 * the BIOS didn't shut down *is* a big problem.
23 */
24
25#define BIOS_LOWMEM_KILOBYTES	0x413
26#define LOWMEM_CAP		0x9f000U	/* Absolute maximum */
27#define INSANE_CUTOFF		0x20000U	/* Less than this = insane */
28
29void __init reserve_ebda_region(void)
30{
31	unsigned int lowmem, ebda_addr;
32
33	/*
34	 * To determine the position of the EBDA and the
35	 * end of conventional memory, we need to look at
36	 * the BIOS data area. In a paravirtual environment
37	 * that area is absent. We'll just have to assume
38	 * that the paravirt case can handle memory setup
39	 * correctly, without our help.
40	 */
41	if (paravirt_enabled())
42		return;
43
44	/* end of low (conventional) memory */
45	lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
46	lowmem <<= 10;
47
48	/* start of EBDA area */
49	ebda_addr = get_bios_ebda();
50
51	/*
52	 * Note: some old Dells seem to need 4k EBDA without
53	 * reporting so, so just consider the memory above 0x9f000
54	 * to be off limits (bugzilla 2990).
55	 */
56
57	/* If the EBDA address is below 128K, assume it is bogus */
58	if (ebda_addr < INSANE_CUTOFF)
59		ebda_addr = LOWMEM_CAP;
60
61	/* If lowmem is less than 128K, assume it is bogus */
62	if (lowmem < INSANE_CUTOFF)
63		lowmem = LOWMEM_CAP;
64
65	/* Use the lower of the lowmem and EBDA markers as the cutoff */
66	lowmem = min(lowmem, ebda_addr);
67	lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */
68
69	/* reserve all memory between lowmem and the 1MB mark */
70	memblock_reserve(lowmem, 0x100000 - lowmem);
71}