linux-kernel - [PATCH 4.2.y-ckt 181/206] s390/vmem: fix identity mapping

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Message-Id: <1465507015-23052-182-git-send-email-kamal@canonical.com>
Date:	Thu,  9 Jun 2016 14:16:30 -0700
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 181/206] s390/vmem: fix identity mapping

4.2.8-ckt12 -stable review patch.  If anyone has any objections, please let me know.

---8<------------------------------------------------------------

From: Heiko Carstens <heiko.carstens@...ibm.com>

commit c34a69059d7876e0793eb410deedfb08ccb22b02 upstream.

The identity mapping is suboptimal for the last 2GB frame. The mapping
will be established with a mix of 4KB and 1MB mappings instead of a
single 2GB mapping.

This happens because of a off-by-one bug introduced with
commit 50be63450728 ("s390/mm: Convert bootmem to memblock").

Currently the identity mapping looks like this:

0x0000000080000000-0x0000000180000000        4G PUD RW
0x0000000180000000-0x00000001fff00000     2047M PMD RW
0x00000001fff00000-0x0000000200000000        1M PTE RW

With the bug fixed it looks like this:

0x0000000080000000-0x0000000200000000        6G PUD RW

Fixes: 50be63450728 ("s390/mm: Convert bootmem to memblock")
Signed-off-by: Heiko Carstens <heiko.carstens@...ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@...ibm.com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
 arch/s390/mm/vmem.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index ef7d6c8..f354fd8 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -372,7 +372,7 @@ void __init vmem_map_init(void)
 	ro_end = (unsigned long)&_eshared & PAGE_MASK;
 	for_each_memblock(memory, reg) {
 		start = reg->base;
-		end = reg->base + reg->size - 1;
+		end = reg->base + reg->size;
 		if (start >= ro_end || end <= ro_start)
 			vmem_add_mem(start, end - start, 0);
 		else if (start >= ro_start && end <= ro_end)
-- 
2.7.4