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    SubjectRe: [RFT] x86 acpi: normalize segment descriptor register on resume
    H. Peter Anvin wrote:
    >
    > The most likely explanation for this is that the VESA BIOS expects to be
    > entered in Big Real Mode (*.limit = 0xffffffff) instead of ordinary Real
    > Mode. Here is a completely untested patch which changes the segment
    > descriptors to Big Real Mode instead. It would be worth testing out.
    >

    ... and here is one that actually has a prayer of actually working.

    -hpa
    diff --git a/arch/x86/kernel/acpi/sleep.c b/arch/x86/kernel/acpi/sleep.c
    index 36af01f..130711f 100644
    --- a/arch/x86/kernel/acpi/sleep.c
    +++ b/arch/x86/kernel/acpi/sleep.c
    @@ -23,6 +23,15 @@ static unsigned long acpi_realmode;
    static char temp_stack[10240];
    #endif

    +/* XXX: this macro should move to asm-x86/segment.h and be shared with the
    + boot code... */
    +#define GDT_ENTRY(flags, base, limit) \
    + (((u64)(base & 0xff000000) << 32) | \
    + ((u64)flags << 40) | \
    + ((u64)(limit & 0x00ff0000) << 32) | \
    + ((u64)(base & 0x00ffffff) << 16) | \
    + ((u64)(limit & 0x0000ffff)))
    +
    /**
    * acpi_save_state_mem - save kernel state
    *
    @@ -58,11 +67,11 @@ int acpi_save_state_mem(void)
    ((char *)&header->wakeup_gdt - (char *)acpi_realmode))
    << 16);
    /* GDT[1]: real-mode-like code segment */
    - header->wakeup_gdt[1] = (0x009bULL << 40) +
    - ((u64)acpi_wakeup_address << 16) + 0xffff;
    + header->wakeup_gdt[1] =
    + GDT_ENTRY(0x809b, acpi_wakeup_address, 0xfffff);
    /* GDT[2]: real-mode-like data segment */
    - header->wakeup_gdt[2] = (0x0093ULL << 40) +
    - ((u64)acpi_wakeup_address << 16) + 0xffff;
    + header->wakeup_gdt[2] =
    + GDT_ENTRY(0x8093, acpi_wakeup_address, 0xfffff);

    #ifndef CONFIG_64BIT
    store_gdt((struct desc_ptr *)&header->pmode_gdt);
    \
     
     \ /
      Last update: 2008-07-14 06:29    [W:0.023 / U:93.112 seconds]
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