s390/uaccess: always load the kernel ASCE after task switch
This patch fixes a problem introduced with git commit beef560b4cdfafb2
"s390/uaccess: simplify control register updates".
The switch_mm function is not called if the next process is a kernel
thread without an attached mm or is a nop if the mm does not change.
But CR1 still needs to be loaded with the kernel ASCE in case the
code returns to a uaccess function that uses the secondary space mode.
In addition move the set_fs call from finish_arch_switch to
finish_arch_post_lock_switch and then remove finish_arch_switch.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/mmu_context.h b/arch/s390/include/asm/mmu_context.h
index c28f32a..3815bfe 100644
--- a/arch/s390/include/asm/mmu_context.h
+++ b/arch/s390/include/asm/mmu_context.h
@@ -33,10 +33,9 @@
static inline void set_user_asce(struct mm_struct *mm)
{
- pgd_t *pgd = mm->pgd;
-
- S390_lowcore.user_asce = mm->context.asce_bits | __pa(pgd);
- set_fs(current->thread.mm_segment);
+ S390_lowcore.user_asce = mm->context.asce_bits | __pa(mm->pgd);
+ if (current->thread.mm_segment.ar4)
+ __ctl_load(S390_lowcore.user_asce, 7, 7);
set_cpu_flag(CIF_ASCE);
}
@@ -70,12 +69,11 @@
/* Clear old ASCE by loading the kernel ASCE. */
__ctl_load(S390_lowcore.kernel_asce, 1, 1);
__ctl_load(S390_lowcore.kernel_asce, 7, 7);
- /* Delay loading of the new ASCE to control registers CR1 & CR7 */
- set_cpu_flag(CIF_ASCE);
atomic_inc(&next->context.attach_count);
atomic_dec(&prev->context.attach_count);
if (MACHINE_HAS_TLB_LC)
cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
+ S390_lowcore.user_asce = next->context.asce_bits | __pa(next->pgd);
}
#define finish_arch_post_lock_switch finish_arch_post_lock_switch
@@ -84,17 +82,18 @@
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;
- if (!mm)
- return;
- preempt_disable();
- while (atomic_read(&mm->context.attach_count) >> 16)
- cpu_relax();
+ load_kernel_asce();
+ if (mm) {
+ preempt_disable();
+ while (atomic_read(&mm->context.attach_count) >> 16)
+ cpu_relax();
- cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
- set_user_asce(mm);
- if (mm->context.flush_mm)
- __tlb_flush_mm(mm);
- preempt_enable();
+ cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
+ if (mm->context.flush_mm)
+ __tlb_flush_mm(mm);
+ preempt_enable();
+ }
+ set_fs(current->thread.mm_segment);
}
#define enter_lazy_tlb(mm,tsk) do { } while (0)
diff --git a/arch/s390/include/asm/switch_to.h b/arch/s390/include/asm/switch_to.h
index 29c81f8..df38c70 100644
--- a/arch/s390/include/asm/switch_to.h
+++ b/arch/s390/include/asm/switch_to.h
@@ -134,8 +134,4 @@
prev = __switch_to(prev,next); \
} while (0)
-#define finish_arch_switch(prev) do { \
- set_fs(current->thread.mm_segment); \
-} while (0)
-
#endif /* __ASM_SWITCH_TO_H */