x86, realmode: Change EFER to a single u64 field

Change EFER to be a single u64 field instead of two u32 fields; change
the order to maintain alignment.  Note that on x86-64 cr4 is really
also a 64-bit quantity, although we can only set the low 32 bits from
the trampoline code since it is still executing in 32-bit mode at that
point.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Jarkko Sakkinen <jarkko.sakkinen@intel.com>

arch/x86/include/asm/realmode.h

@@ -35,9 +35,8 @@ struct trampoline_header {
 	u32 gdt_base;
 #else
 	u64 start;
+	u64 efer;
 	u32 cr4;
-	u32 efer_low;
-	u32 efer_high;
 #endif
 };
 

arch/x86/realmode/init.c

@@ -22,7 +22,7 @@ void __init setup_real_mode(void)
 	size_t size = PAGE_ALIGN(real_mode_blob_end - real_mode_blob);
 #ifdef CONFIG_X86_64
 	u64 *trampoline_pgd;
-	u32 efer_low, efer_high;
+	u64 efer;
 #endif
 
 	/* Has to be in very low memory so we can execute real-mode AP code. */
@@ -70,9 +70,8 @@ void __init setup_real_mode(void)
 	 * Some AMD processors will #GP(0) if EFER.LMA is set in WRMSR
 	 * so we need to mask it out.
 	 */
-	rdmsr(MSR_EFER, efer_low, efer_high);
-	trampoline_header->efer_low  = efer_low & ~EFER_LMA;
-	trampoline_header->efer_high = efer_high;
+	rdmsrl(MSR_EFER, efer);
+	trampoline_header->efer = efer & ~EFER_LMA;
 
 	trampoline_header->start = (u64) secondary_startup_64;
 	trampoline_cr4_features = &trampoline_header->cr4;

arch/x86/realmode/rm/trampoline_64.S

@@ -146,8 +146,8 @@ GLOBAL(trampoline_pgd)		.space	PAGE_SIZE
 	.balign	8
 GLOBAL(trampoline_header)
 	tr_start:		.space	8
-	GLOBAL(tr_cr4)		.space	4
 	GLOBAL(tr_efer)		.space	8
+	GLOBAL(tr_cr4)		.space	4
 END(trampoline_header)
 
 #include "trampoline_common.S"