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authorDominik Dingel <dingel@linux.vnet.ibm.com>2015-06-25 14:59:39 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-06-25 17:00:35 -0700
commitbea41197ead3e03308bdd10c11db3ce91ae5c8ab (patch)
treed05c10b8364ee6a1892c9d613ed16cec70897f7f /arch/s390/kernel
parentaefbef10e3ae6e2c6e3c54f906f10b34c73a2c66 (diff)
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>
Diffstat (limited to 'arch/s390/kernel')
-rw-r--r--arch/s390/kernel/setup.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/arch/s390/kernel/setup.c b/arch/s390/kernel/setup.c
index af4f41d52cde..73941bf42350 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.
*/