[PATCH] x86/mm: Limit 2/4M size calculation to x86_32

[Stefan Bader]

commit 722bc6b (x86/mm: Fix the size calculation of mapping tables)
did modify the extra space calculation for mapping tables in order
to make up for the first 2/4M memory range using 4K pages.
However this setup is only used when compiling for 32bit. On 64bit
there is only the trailing area of 4K pages (which is already added).

The code was already adapted once for things went wrong on a 8TB
machine (bd2753b x86/mm: Only add extra pages count for the first memory
range during pre-allocation early page table space), but it looks a bit
like it currently would overdo things for 64bit.
I only noticed while bisecting for the reason I could not make a crash
kernel boot (which ended up on this patch).

Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v3.5
Cc: WANG Cong <xiyou.wangcong@xxxxxxxxx>
Cc: Yinghai Lu <yinghai@xxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
---
 arch/x86/mm/init.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index e0e6990..28a1c99 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -60,10 +60,11 @@ static void __init find_early_table_space(struct map_range *mr, unsigned long en
 		extra = end - ((end>>PMD_SHIFT) << PMD_SHIFT);
 #ifdef CONFIG_X86_32
 		extra += PMD_SIZE;
-#endif
+
 		/* The first 2/4M doesn't use large pages. */
 		if (mr->start < PMD_SIZE)
 			extra += mr->end - mr->start;
+#endif
 
 		ptes = (extra + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	} else
-- 
1.7.10.4

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