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.
Acked-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
Signed-off-by: Dominik Dingel <dingel@xxxxxxxxxxxxxxxxxx>
---
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 53eacbd..0844b78 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 a5ea8bc..9ac282b 100644
--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -915,6 +915,8 @@ 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 b2c1542..f76791e 100644
--- a/arch/s390/mm/pgtable.c
+++ b/arch/s390/mm/pgtable.c
@@ -36,6 +36,8 @@
#endif
+unsigned int HPAGE_SHIFT;
+
unsigned long *crst_table_alloc(struct mm_struct *mm)
{
struct page *page = alloc_pages(GFP_KERNEL, ALLOC_ORDER);
--
2.3.7
