Enter 64-bit mode as early as possible in the 64-bit PowerPC boot sequence.

Most of the effect of setting MSR[SF] is that the CPU will stop ignoring
the high 32 bits of registers containing addresses in load/store
instructions. As such, the kernel was setting it only when it began to
need access to high memory. MSR[SF] also affects the operation of some
conditional instructions, however, and so setting it at late times could
subtly break code at very early times. This fixes use of the FDT mode in
loader, and FDT boot more generally, on 64-bit PowerPC systems.

Hardware provided by: IBM LTC
Approved by: re (kib)

sys/powerpc/aim/aim_machdep.c

@@ -179,17 +179,6 @@ aim_cpu_init(vm_offset_t toc)
 	trap_offset = 0;
 	cacheline_warn = 0;
 
-	#ifdef __powerpc64__
-	/*
-	 * Switch to 64-bit mode, if the bootloader didn't, before we start 
-	 * using memory beyond what the bootloader might have set up.
-	 * Guaranteed not to cause an implicit branch since we either (a)
-	 * started with a 32-bit bootloader below 4 GB or (b) were already in
-	 * 64-bit mode, making this a no-op.
-	 */
-	mtmsrd(mfmsr() | PSL_SF);
-	#endif
-
 	/* Various very early CPU fix ups */
 	switch (mfpvr() >> 16) {
 		/*

sys/powerpc/aim/locore64.S

@@ -76,6 +76,14 @@ btext:
  */
 	.text
 ASENTRY_NOPROF(__start)
+	/* Set 64-bit mode if not yet set before branching to C */
+	mfmsr	%r20
+	li	%r21,1
+	insrdi	%r20,%r21,1,0
+	mtmsrd	%r20
+	isync
+	nop	/* Make this block a multiple of 8 bytes */
+
 	/* Set up the TOC pointer */
 	b	0f
 	.align 3