As Christian pointed out, the recent 'Revert "thp: make MADV_HUGEPAGE
check for mm->def_flags"' breaks qemu, it does QEMU_MADV_HUGEPAGE for
all kvm pages but this doesn't work after s390_enable_sie/thp_split_mm.
Paolo suggested that instead of failing on the call to madvise, we
simply ignore the call (return 0).
Reported-by: Christian Borntraeger <borntrae...@de.ibm.com>
Suggested-by: Paolo Bonzini <pbonz...@redhat.com>
Suggested-by: Oleg Nesterov <o...@redhat.com>
Signed-off-by: Alex Thorlton <athorl...@sgi.com>
Cc: Gerald Schaefer <gerald.schae...@de.ibm.com>
Cc: Martin Schwidefsky <schwidef...@de.ibm.com>
Cc: Heiko Carstens <heiko.carst...@de.ibm.com>
Cc: Christian Borntraeger <borntrae...@de.ibm.com>
Cc: Andrew Morton <a...@linux-foundation.org>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shute...@linux.intel.com>
Cc: Mel Gorman <mgor...@suse.de>
Cc: Rik van Riel <r...@redhat.com>
Cc: Ingo Molnar <mi...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Andrea Arcangeli <aarca...@redhat.com>
Cc: Oleg Nesterov <o...@redhat.com>
Cc: "Eric W. Biederman" <ebied...@xmission.com>
Cc: Alexander Viro <v...@zeniv.linux.org.uk>
Cc: linux...@de.ibm.com
Cc: linux-s...@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux...@kvack.org
Cc: linux-...@vger.kernel.org
---
mm/huge_memory.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index a4310a5..61d234d 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1970,6 +1970,15 @@ int hugepage_madvise(struct vm_area_struct *vma,
{
switch (advice) {
case MADV_HUGEPAGE:
+#ifdef CONFIG_S390
+ /*
+ * qemu blindly sets MADV_HUGEPAGE on all allocations, but s390
+ * can't handle this properly after s390_enable_sie, so we
simply
+ * ignore the madvise to prevent qemu from causing a SIGSEGV.
+ */
+ if (mm_has_pgste(vma->vm_mm))
+ return 0;
+#endif
/*
* Be somewhat over-protective like KSM for now!
*/
--
1.7.12.4
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