From bea41197ead3e03308bdd10c11db3ce91ae5c8ab Mon Sep 17 00:00:00 2001
From: Dominik Dingel <dingel@linux.vnet.ibm.com>
Date: Thu, 25 Jun 2015 14:59:39 -0700
Subject: [PATCH] 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>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@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 --git a/arch/s390/include/asm/page.h b/arch/s390/include/asm/page.h
index 53eacbd4f09bf..0844b780c6a44 100644
--- a/arch/s390/include/asm/page.h
+++ b/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 --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index af4f41d52cde5..73941bf423508 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -880,6 +880,8 @@ 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 --git a/arch/s390/mm/pgtable.c b/arch/s390/mm/pgtable.c
index b33f66110ca94..16154720bdb60 100644
--- a/arch/s390/mm/pgtable.c
+++ b/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);
--
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