+ s390-mm-make-hugepages_supported-a-boot-time-decision.patch added to -mm tree

+ s390-mm-make-hugepages_supported-a-boot-time-decision.patch added to -mm tree

[akpm]

The patch titled
     Subject: s390/mm: make hugepages_supported a boot time decision
has been added to the -mm tree.  Its filename is
     s390-mm-make-hugepages_supported-a-boot-time-decision.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/s390-mm-make-hugepages_supported-a-boot-time-decision.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/s390-mm-make-hugepages_supported-a-boot-time-decision.patch

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------------------------------------------------------
From: Dominik Dingel <dingel@linux.vnet.ibm.com>
Subject: s390/mm: make hugepages_supported a boot time decision

There is a potential bug with KVM and hugetlbfs if the hardware does not
support hugepages (EDAT1).  We fix this by making EDAT1 a hard requirement
for hugepages and therefore removing and simplifying code.

As s390, with the sw-emulated hugepages, was the only user of
arch_prepare/release_hugepage I also removed theses calls from common and
other architecture code.


This patch (of 5):

By dropping support for hugepages on machines which do not have the
hardware feature EDAT1, we fix a potential s390 KVM bug.

The bug would happen if a guest is backed by hugetlbfs (not supported
currently), but does not get pagetables with PGSTE.  This would lead to
random memory overwrites.

Signed-off-by: Dominik Dingel <dingel@linux.vnet.ibm.com>
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/s390/include/asm/page.h |    8 ++++----
 arch/s390/kernel/setup.c     |    2 ++
 arch/s390/mm/pgtable.c       |    2 ++
 3 files changed, 8 insertions(+), 4 deletions(-)

diff -puN arch/s390/include/asm/page.h~s390-mm-make-hugepages_supported-a-boot-time-decision arch/s390/include/asm/page.h
--- a/arch/s390/include/asm/page.h~s390-mm-make-hugepages_supported-a-boot-time-decision
+++ a/arch/s390/include/asm/page.h
@@ -17,7 +17,10 @@
 #define PAGE_DEFAULT_ACC	0
 #define PAGE_DEFAULT_KEY	(PAGE_DEFAULT_ACC << 4)
 
-#define HPAGE_SHIFT	20
+#include <asm/setup.h>
+#ifndef __ASSEMBLY__
+
+extern unsigned int HPAGE_SHIFT;
 #define HPAGE_SIZE	(1UL << HPAGE_SHIFT)
 #define HPAGE_MASK	(~(HPAGE_SIZE - 1))
 #define HUGETLB_PAGE_ORDER	(HPAGE_SHIFT - PAGE_SHIFT)
@@ -27,9 +30,6 @@
 #define ARCH_HAS_PREPARE_HUGEPAGE
 #define ARCH_HAS_HUGEPAGE_CLEAR_FLUSH
 
-#include <asm/setup.h>
-#ifndef __ASSEMBLY__
-
 static inline void storage_key_init_range(unsigned long start, unsigned long end)
 {
 #if PAGE_DEFAULT_KEY
diff -puN arch/s390/kernel/setup.c~s390-mm-make-hugepages_supported-a-boot-time-decision arch/s390/kernel/setup.c
--- a/arch/s390/kernel/setup.c~s390-mm-make-hugepages_supported-a-boot-time-decision
+++ a/arch/s390/kernel/setup.c
@@ -875,6 +875,8 @@ void __init setup_arch(char **cmdline_p)
 	 */
 	setup_hwcaps();
 
+	HPAGE_SHIFT = MACHINE_HAS_HPAGE ? 20 : 0;
+
 	/*
 	 * Create kernel page tables and switch to virtual addressing.
 	 */
diff -puN arch/s390/mm/pgtable.c~s390-mm-make-hugepages_supported-a-boot-time-decision arch/s390/mm/pgtable.c
--- a/arch/s390/mm/pgtable.c~s390-mm-make-hugepages_supported-a-boot-time-decision
+++ a/arch/s390/mm/pgtable.c
@@ -31,6 +31,8 @@
 #define ALLOC_ORDER	2
 #define FRAG_MASK	0x03
 
+unsigned int HPAGE_SHIFT;
+
 unsigned long *crst_table_alloc(struct mm_struct *mm)
 {
 	struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
_

Patches currently in -mm which might be from dingel@linux.vnet.ibm.com are

s390-mm-make-hugepages_supported-a-boot-time-decision.patch
mm-hugetlb-remove-unused-arch-hook-prepare-release_hugepage.patch
mm-hugetlb-remove-arch_prepare-release_hugepage-from-arch-headers.patch
s390-hugetlb-remove-dead-code-for-sw-emulated-huge-pages.patch
s390-mm-forward-check-for-huge-pmds-to-pmd_large.patch
linux-next.patch