x86, range: fix missing merge during add range

Christian found v3.9 does not work with E350 with EFI is enabled.

[    1.658832] Trying to unpack rootfs image as initramfs...
[    1.679935] BUG: unable to handle kernel paging request at ffff88006e3fd000
[    1.686940] IP: [<ffffffff813661df>] memset+0x1f/0xb0
[    1.692010] PGD 1f77067 PUD 1f7a067 PMD 61420067 PTE 0

but early memtest report all memory could be accessed without problem.

early page table is set in following sequence:
[    0.000000] init_memory_mapping: [mem 0x00000000-0x000fffff]
[    0.000000] init_memory_mapping: [mem 0x6e600000-0x6e7fffff]
[    0.000000] init_memory_mapping: [mem 0x6c000000-0x6e5fffff]
[    0.000000] init_memory_mapping: [mem 0x00100000-0x6bffffff]
[    0.000000] init_memory_mapping: [mem 0x6e800000-0x6ea07fff]
but later efi_enter_virtual_mode try set mapping again wrongly.
[    0.010644] pid_max: default: 32768 minimum: 301
[    0.015302] init_memory_mapping: [mem 0x640c5000-0x6e3fcfff]
that means it fails with pfn_range_is_mapped.

It turns out that we have a bug in add_range_with_merge and it does not
merge range properly when new add one fill the hole between two exsiting
ranges. In the case when [mem 0x00100000-0x6bffffff] is the hole between
[mem 0x00000000-0x000fffff] and [mem 0x6c000000-0x6e7fffff].

Fix the add_range_with_merge by calling itself recursively.
Reported-by: "Christian König" <christian.koenig@amd.com>
Signed-off-by: Yinghai Lu <yinghai@kernel.org>
Link: http://lkml.kernel.org/r/CAE9FiQVofGoSk7q5-0irjkBxemqK729cND4hov-1QCBJDhxpgQ@mail.gmail.com
Cc: <stable@vger.kernel.org> v3.9
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

kernel/range.c

@@ -48,9 +48,11 @@ int add_range_with_merge(struct range *range, int az, int nr_range,
 		final_start = min(range[i].start, start);
 		final_end = max(range[i].end, end);
 
-		range[i].start = final_start;
-		range[i].end =  final_end;
-		return nr_range;
+		/* clear it and add it back for further merge */
+		range[i].start = 0;
+		range[i].end =  0;
+		return add_range_with_merge(range, az, nr_range,
+			final_start, final_end);
 	}
 
 	/* Need to add it: */