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s390/mm: fix local TLB flushing vs. detach of an mm address space 

The local TLB flushing code keeps an additional mask in the mm.context,
the cpu_attach_mask. At the time a global flush of an address space is
done the cpu_attach_mask is copied to the mm_cpumask in order to avoid
future global flushes in case the mm is used by a single CPU only after
the flush.

Trouble is that the reset of the mm_cpumask is racy against the detach
of an mm address space by switch_mm. The current order is first the
global TLB flush and then the copy of the cpu_attach_mask to the
mm_cpumask. The order needs to be the other way around.

Cc: <stable@vger.kernel.org>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky 2017-08-16 14:10:01 +02:00
parent 46fde9a9d2
commit b3e5dc45fd
2 changed files with 7 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/s390/include/asm/mmu_context.h
View File

@ -103,7 +103,6 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
if (prev == next) if (prev == next)
return; return;
cpumask_set_cpu(cpu, &next->context.cpu_attach_mask); cpumask_set_cpu(cpu, &next->context.cpu_attach_mask);
cpumask_set_cpu(cpu, mm_cpumask(next));
/* Clear old ASCE by loading the kernel ASCE. */ /* Clear old ASCE by loading the kernel ASCE. */
__ctl_load(S390_lowcore.kernel_asce, 1, 1); __ctl_load(S390_lowcore.kernel_asce, 1, 1);
__ctl_load(S390_lowcore.kernel_asce, 7, 7); __ctl_load(S390_lowcore.kernel_asce, 7, 7);
@ -121,7 +120,7 @@ static inline void finish_arch_post_lock_switch(void)
preempt_disable(); preempt_disable();
while (atomic_read(&mm->context.flush_count)) while (atomic_read(&mm->context.flush_count))
cpu_relax(); cpu_relax();
cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
if (mm->context.flush_mm) if (mm->context.flush_mm)
__tlb_flush_mm(mm); __tlb_flush_mm(mm);
preempt_enable(); preempt_enable();
@ -136,6 +135,7 @@ static inline void activate_mm(struct mm_struct *prev,
struct mm_struct *next) struct mm_struct *next)
{ {
switch_mm(prev, next, current); switch_mm(prev, next, current);
cpumask_set_cpu(smp_processor_id(), mm_cpumask(next));
set_user_asce(next); set_user_asce(next);
} }

26
arch/s390/include/asm/tlbflush.h
View File

@ -48,23 +48,6 @@ static inline void __tlb_flush_global(void)
* Flush TLB entries for a specific mm on all CPUs (in case gmap is used * Flush TLB entries for a specific mm on all CPUs (in case gmap is used
* this implicates multiple ASCEs!). * this implicates multiple ASCEs!).
*/ */
static inline void __tlb_flush_full(struct mm_struct *mm)
{
preempt_disable();
atomic_inc(&mm->context.flush_count);
if (cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id()))) {
/* Local TLB flush */
__tlb_flush_local();
} else {
/* Global TLB flush */
__tlb_flush_global();
/* Reset TLB flush mask */
cpumask_copy(mm_cpumask(mm), &mm->context.cpu_attach_mask);
}
atomic_dec(&mm->context.flush_count);
preempt_enable();
}
static inline void __tlb_flush_mm(struct mm_struct *mm) static inline void __tlb_flush_mm(struct mm_struct *mm)
{ {
unsigned long gmap_asce; unsigned long gmap_asce;
@ -76,16 +59,18 @@ static inline void __tlb_flush_mm(struct mm_struct *mm)
*/ */
preempt_disable(); preempt_disable();
atomic_inc(&mm->context.flush_count); atomic_inc(&mm->context.flush_count);
/* Reset TLB flush mask */
cpumask_copy(mm_cpumask(mm), &mm->context.cpu_attach_mask);
barrier();
gmap_asce = READ_ONCE(mm->context.gmap_asce); gmap_asce = READ_ONCE(mm->context.gmap_asce);
if (MACHINE_HAS_IDTE && gmap_asce != -1UL) { if (MACHINE_HAS_IDTE && gmap_asce != -1UL) {
if (gmap_asce) if (gmap_asce)
__tlb_flush_idte(gmap_asce); __tlb_flush_idte(gmap_asce);
__tlb_flush_idte(mm->context.asce); __tlb_flush_idte(mm->context.asce);
} else { } else {
__tlb_flush_full(mm); /* Global TLB flush */
__tlb_flush_global();
} }
/* Reset TLB flush mask */
cpumask_copy(mm_cpumask(mm), &mm->context.cpu_attach_mask);
atomic_dec(&mm->context.flush_count); atomic_dec(&mm->context.flush_count);
preempt_enable(); preempt_enable();
} }
@ -99,7 +84,6 @@ static inline void __tlb_flush_kernel(void)
} }
#else #else
#define __tlb_flush_global() __tlb_flush_local() #define __tlb_flush_global() __tlb_flush_local()
#define __tlb_flush_full(mm) __tlb_flush_local()
/* /*
* Flush TLB entries for a specific ASCE on all CPUs. * Flush TLB entries for a specific ASCE on all CPUs.