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Commit f8b13505 authored by Martin Schwidefsky's avatar Martin Schwidefsky
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s390/uaccess: always load the kernel ASCE after task switch 



This patch fixes a problem introduced with git commit beef560b
"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: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent c1a42f49

arch/s390/include/asm/mmu_context.h

+16 −17
Original line number Diff line number Diff line
@@ -33,10 +33,9 @@ static inline int init_new_context(struct task_struct *tsk, 


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 @@ static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, 
	/* 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
@@ -84,18 +82,19 @@ static inline void finish_arch_post_lock_switch(void) 
	struct task_struct *tsk = current;

	struct mm_struct *mm = tsk->mm;



	if (!mm)

		return;

	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();

	}

	set_fs(current->thread.mm_segment);

}



#define enter_lazy_tlb(mm,tsk)	do { } while (0)

#define deactivate_mm(tsk,mm)	do { } while (0)

arch/s390/include/asm/switch_to.h

+0 −4
Original line number Diff line number Diff line
@@ -134,8 +134,4 @@ static inline void restore_access_regs(unsigned int *acrs) 
	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 */