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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);
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