Re: [RFT] x86 acpi: normalize segment descriptor register on resume

["H. Peter Anvin" <hpa@zytor.com>]

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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

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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);