[PATCH] ppc64: Move Initrd

From: Rusty Russell <rusty@rustcorp.com.au>

This patch moves the initrd when "make_room" runs out of space, rather than
stepping over it.  The problem with stepping over it is that it gets copied
with the kernel when this happens, which wastes space.

Also ensures that the initrd isn't where the kernel wants to be moved to: if
it is, it gets moved out the way.

arch/ppc64/kernel/prom.c

@@ -1539,7 +1539,7 @@ static unsigned long __init check_display(unsigned long mem)
 	return DOUBLEWORD_ALIGN(mem);
 }
 
-/* Return (relocated) pointer to this much memory: skips initrd if any. */
+/* Return (relocated) pointer to this much memory: moves initrd if reqd. */
 static void __init *__make_room(unsigned long *mem_start, unsigned long *mem_end,
 				unsigned long needed, unsigned long align)
 {
@@ -1548,11 +1548,21 @@ static void __init *__make_room(unsigned long *mem_start, unsigned long *mem_end
 
 	*mem_start = ALIGN(*mem_start, align);
 	if (*mem_start + needed > *mem_end) {
+		/* FIXME: Apple OF doesn't map unclaimed mem.  If this
+		 * ever happened on G5, we'd need to fix. */
+		unsigned long initrd_len;
+
 		if (*mem_end != RELOC(initrd_start))
 			prom_panic(RELOC("No memory for copy_device_tree"));
-		*mem_start = RELOC(initrd_end);
-		/* We can't pass huge values to OF, so use 1G. */
-		*mem_end = *mem_start + 1024*1024*1024;
+
+		prom_print("Huge device_tree: moving initrd\n");
+		/* Move by 4M. */
+		initrd_len = RELOC(initrd_end) - RELOC(initrd_start);
+		*mem_end = RELOC(initrd_start) + 4 * 1024 * 1024;
+		memmove((void *)*mem_end, (void *)RELOC(initrd_start),
+			initrd_len);
+		RELOC(initrd_start) = *mem_end;
+		RELOC(initrd_end) = RELOC(initrd_start) + initrd_len;
 	}
 
 	ret = (void *)*mem_start;
@@ -1977,10 +1987,22 @@ prom_init(unsigned long r3, unsigned long r4, unsigned long pp,
 #endif /* DEBUG_PROM */
 
 	lmb_reserve(0, __pa(RELOC(klimit)));
+
 #ifdef CONFIG_BLK_DEV_INITRD
-	/* If this didn't cover the initrd, do so now */
-	if (mem < RELOC(initrd_start))
-		lmb_reserve(RELOC(initrd_start), RELOC(initrd_end) - RELOC(initrd_start));
+	if (RELOC(initrd_start)) {
+		unsigned long initrd_len;
+		initrd_len = RELOC(initrd_end) - RELOC(initrd_start);
+
+		/* Move initrd if it's where we're going to copy kernel. */
+		if (RELOC(initrd_start) < __pa(RELOC(klimit))) {
+			memmove((void *)mem, (void *)RELOC(initrd_start),
+				initrd_len);
+			RELOC(initrd_start) = mem;
+			RELOC(initrd_end) = mem + initrd_len;
+		}
+
+		lmb_reserve(RELOC(initrd_start), initrd_len);
+	}
 #endif /* CONFIG_BLK_DEV_INITRD */
 
 	if (_systemcfg->platform == PLATFORM_PSERIES)