#include <linux/kernel.h> #include <linux/init.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 */ reserve_early_overlap_ok(lowmem, 0x100000, "BIOS reserved"); }