diff options
Diffstat (limited to 'arch/x86')
| -rw-r--r-- | arch/x86/kernel/head64.c | 45 |
1 files changed, 27 insertions, 18 deletions
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 38f32e798a99..b684552347df 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -49,33 +49,42 @@ static void __init copy_bootdata(char *real_mode_data) } } -#define EBDA_ADDR_POINTER 0x40E +#define BIOS_EBDA_SEGMENT 0x40E +#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. + */ static __init void reserve_ebda(void) { - unsigned ebda_addr, ebda_size; + unsigned int lowmem, ebda_addr; - /* - * there is a real-mode segmented pointer pointing to the - * 4K EBDA area at 0x40E - */ - ebda_addr = *(unsigned short *)__va(EBDA_ADDR_POINTER); + /* 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; - if (!ebda_addr) - return; + /* 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; - ebda_size = *(unsigned short *)__va(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; - /* Round EBDA up to pages */ - if (ebda_size == 0) - ebda_size = 1; - ebda_size <<= 10; - ebda_size = round_up(ebda_size + (ebda_addr & ~PAGE_MASK), PAGE_SIZE); - if (ebda_size > 64*1024) - ebda_size = 64*1024; + /* Paranoia: should never happen, but... */ + if (lowmem >= 0x100000) + lowmem = 0xa0000; - reserve_early(ebda_addr, ebda_addr + ebda_size, "EBDA"); + /* reserve all memory between lowmem and the 1MB mark */ + reserve_early(lowmem, 0x100000, "BIOS reserved"); } void __init x86_64_start_kernel(char * real_mode_data) |