Question: Will Linux kernel disable acess to Legacy VGA Mem (0xA0000 - 0xBFFFF)

cmicboy

Recently I met a problem when run some GPU/CPU test on Ubuntu12.04. The tests are failing when boot with EFI Ubuntu hard disk, but passing when boot with legacy Ubuntu hard disk.

Basically I suspect kernel disabled access to memory range 0xA0000 – 0xBFFFF, but I have no evidence.

I am not familiar with kernel code, only thing I found is below snippet in kernel. Would someone know the answer?

# if defined(CONFIG_VGA_CONSOLE)
        /*
        * Non-legacy systems may route legacy VGA MMIO range to system
        * memory.  vga_con probes the MMIO hole, so memory looks like
        * a VGA device to it.  The EFI memory map can tell us if it's
        * memory so we can avoid this problem.
        */
        if (efi_mem_type(0xA0000) != EFI_CONVENTIONAL_MEMORY)
            conswitchp = &vga_con;
# endif

webdna

我想是内存不够原因