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s390/mm: fix flush_tlb_kernel_range()

commit f6a70a0 upstream.

Our flush_tlb_kernel_range() implementation calls __tlb_flush_mm() with
&init_mm as argument. __tlb_flush_mm() however will only flush tlbs
for the passed in mm if its mm_cpumask is not empty.

For the init_mm however its mm_cpumask has never any bits set. Which in
turn means that our flush_tlb_kernel_range() implementation doesn't
work at all.

This can be easily verified with a vmalloc/vfree loop which allocates
a page, writes to it and then frees the page again. A crash will follow
almost instantly.

To fix this remove the cpumask_empty() check in __tlb_flush_mm() since
there shouldn't be too many mms with a zero mm_cpumask, besides the
init_mm of course.

Signed-off-by: Heiko Carstens <>
Signed-off-by: Martin Schwidefsky <>
Signed-off-by: Ben Hutchings <>
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1 parent 0f6dbeb commit 5114f70796dbc6151443778679973f5f33bc4336 @heicarst heicarst committed with bwhacks Mar 4, 2013
Showing with 0 additions and 2 deletions.
  1. +0 −2 arch/s390/include/asm/tlbflush.h
@@ -74,8 +74,6 @@ static inline void __tlb_flush_idte(unsigned long asce)
static inline void __tlb_flush_mm(struct mm_struct * mm)
- if (unlikely(cpumask_empty(mm_cpumask(mm))))
- return;
* If the machine has IDTE we prefer to do a per mm flush
* on all cpus instead of doing a local flush if the mm

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