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s390/uaccess: simplify control register updates
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Always switch to the kernel ASCE in switch_mm. Load the secondary
space ASCE in finish_arch_post_lock_switch after checking that
any pending page table operations have completed. The primary
ASCE is loaded in entry[64].S. With this the update_primary_asce
call can be removed from the switch_to macro and from the start
of switch_mm function. Remove the load_primary argument from
update_user_asce/clear_user_asce, rename update_user_asce to
set_user_asce and rename update_primary_asce to load_kernel_asce.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
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Martin Schwidefsky committed May 20, 2014
1 parent f4192bf commit beef560
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Showing 8 changed files with 33 additions and 43 deletions.
4 changes: 2 additions & 2 deletions arch/s390/include/asm/futex.h
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,7 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr)
int cmparg = (encoded_op << 20) >> 20;
int oldval = 0, newval, ret;

update_primary_asce(current);
load_kernel_asce();
if (encoded_op & (FUTEX_OP_OPARG_SHIFT << 28))
oparg = 1 << oparg;

Expand Down Expand Up @@ -79,7 +79,7 @@ static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
{
int ret;

update_primary_asce(current);
load_kernel_asce();
asm volatile(
" sacf 256\n"
"0: cs %1,%4,0(%5)\n"
Expand Down
43 changes: 17 additions & 26 deletions arch/s390/include/asm/mmu_context.h
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Original file line number Diff line number Diff line change
Expand Up @@ -30,59 +30,49 @@ static inline int init_new_context(struct task_struct *tsk,

#define destroy_context(mm) do { } while (0)

static inline void update_user_asce(struct mm_struct *mm, int load_primary)
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);
if (load_primary)
__ctl_load(S390_lowcore.user_asce, 1, 1);
set_fs(current->thread.mm_segment);
set_thread_flag(TIF_ASCE);
}

static inline void clear_user_asce(struct mm_struct *mm, int load_primary)
static inline void clear_user_asce(void)
{
S390_lowcore.user_asce = S390_lowcore.kernel_asce;

if (load_primary)
__ctl_load(S390_lowcore.user_asce, 1, 1);
__ctl_load(S390_lowcore.user_asce, 1, 1);
__ctl_load(S390_lowcore.user_asce, 7, 7);
}

static inline void update_primary_asce(struct task_struct *tsk)
static inline void load_kernel_asce(void)
{
unsigned long asce;

__ctl_store(asce, 1, 1);
if (asce != S390_lowcore.kernel_asce)
__ctl_load(S390_lowcore.kernel_asce, 1, 1);
set_tsk_thread_flag(tsk, TIF_ASCE);
set_thread_flag(TIF_ASCE);
}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
int cpu = smp_processor_id();

update_primary_asce(tsk);
if (prev == next)
return;
if (MACHINE_HAS_TLB_LC)
cpumask_set_cpu(cpu, &next->context.cpu_attach_mask);
if (atomic_inc_return(&next->context.attach_count) >> 16) {
/* Delay update_user_asce until all TLB flushes are done. */
set_tsk_thread_flag(tsk, TIF_TLB_WAIT);
/* Clear old ASCE by loading the kernel ASCE. */
clear_user_asce(next, 0);
} else {
cpumask_set_cpu(cpu, mm_cpumask(next));
update_user_asce(next, 0);
if (next->context.flush_mm)
/* Flush pending TLBs */
__tlb_flush_mm(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_thread_flag(TIF_ASCE);
atomic_inc(&next->context.attach_count);
atomic_dec(&prev->context.attach_count);
WARN_ON(atomic_read(&prev->context.attach_count) < 0);
if (MACHINE_HAS_TLB_LC)
cpumask_clear_cpu(cpu, &prev->context.cpu_attach_mask);
}
Expand All @@ -93,15 +83,14 @@ static inline void finish_arch_post_lock_switch(void)
struct task_struct *tsk = current;
struct mm_struct *mm = tsk->mm;

if (!test_tsk_thread_flag(tsk, TIF_TLB_WAIT))
if (!mm)
return;
preempt_disable();
clear_tsk_thread_flag(tsk, TIF_TLB_WAIT);
while (atomic_read(&mm->context.attach_count) >> 16)
cpu_relax();

cpumask_set_cpu(smp_processor_id(), mm_cpumask(mm));
update_user_asce(mm, 0);
set_user_asce(mm);
if (mm->context.flush_mm)
__tlb_flush_mm(mm);
preempt_enable();
Expand All @@ -113,7 +102,9 @@ static inline void finish_arch_post_lock_switch(void)
static inline void activate_mm(struct mm_struct *prev,
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);
}

static inline void arch_dup_mmap(struct mm_struct *oldmm,
Expand Down
1 change: 0 additions & 1 deletion arch/s390/include/asm/switch_to.h
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Original file line number Diff line number Diff line change
Expand Up @@ -132,7 +132,6 @@ static inline void restore_access_regs(unsigned int *acrs)
update_cr_regs(next); \
} \
prev = __switch_to(prev,next); \
update_primary_asce(current); \
} while (0)

#define finish_arch_switch(prev) do { \
Expand Down
4 changes: 1 addition & 3 deletions arch/s390/include/asm/thread_info.h
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Original file line number Diff line number Diff line change
Expand Up @@ -81,8 +81,7 @@ static inline struct thread_info *current_thread_info(void)
#define TIF_NOTIFY_RESUME 1 /* callback before returning to user */
#define TIF_SIGPENDING 2 /* signal pending */
#define TIF_NEED_RESCHED 3 /* rescheduling necessary */
#define TIF_TLB_WAIT 4 /* wait for TLB flush completion */
#define TIF_ASCE 5 /* primary asce needs fixup / uaccess */
#define TIF_ASCE 5 /* user asce needs fixup / uaccess */
#define TIF_PER_TRAP 6 /* deliver sigtrap on return to user */
#define TIF_MCCK_PENDING 7 /* machine check handling is pending */
#define TIF_SYSCALL_TRACE 8 /* syscall trace active */
Expand All @@ -99,7 +98,6 @@ static inline struct thread_info *current_thread_info(void)
#define _TIF_NOTIFY_RESUME (1<<TIF_NOTIFY_RESUME)
#define _TIF_SIGPENDING (1<<TIF_SIGPENDING)
#define _TIF_NEED_RESCHED (1<<TIF_NEED_RESCHED)
#define _TIF_TLB_WAIT (1<<TIF_TLB_WAIT)
#define _TIF_ASCE (1<<TIF_ASCE)
#define _TIF_PER_TRAP (1<<TIF_PER_TRAP)
#define _TIF_MCCK_PENDING (1<<TIF_MCCK_PENDING)
Expand Down
2 changes: 1 addition & 1 deletion arch/s390/kernel/entry.S
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
_TIF_MCCK_PENDING | _TIF_ASCE)
_TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
_TIF_SYSCALL_TRACEPOINT)
_TIF_TRANSFER = (_TIF_MCCK_PENDING | _TIF_TLB_WAIT)
_TIF_TRANSFER = (_TIF_MCCK_PENDING | _TIF_ASCE)

STACK_SHIFT = PAGE_SHIFT + THREAD_ORDER
STACK_SIZE = 1 << STACK_SHIFT
Expand Down
2 changes: 1 addition & 1 deletion arch/s390/kernel/entry64.S
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ _TIF_WORK_INT = (_TIF_SIGPENDING | _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED | \
_TIF_MCCK_PENDING | _TIF_ASCE)
_TIF_TRACE = (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | _TIF_SECCOMP | \
_TIF_SYSCALL_TRACEPOINT)
_TIF_TRANSFER = (_TIF_MCCK_PENDING | _TIF_TLB_WAIT)
_TIF_TRANSFER = (_TIF_MCCK_PENDING | _TIF_ASCE)

#define BASED(name) name-system_call(%r13)

Expand Down
10 changes: 5 additions & 5 deletions arch/s390/lib/uaccess.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ static inline unsigned long copy_from_user_mvcp(void *x, const void __user *ptr,
{
unsigned long tmp1, tmp2;

update_primary_asce(current);
load_kernel_asce();
tmp1 = -256UL;
asm volatile(
" sacf 0\n"
Expand Down Expand Up @@ -159,7 +159,7 @@ static inline unsigned long copy_to_user_mvcs(void __user *ptr, const void *x,
{
unsigned long tmp1, tmp2;

update_primary_asce(current);
load_kernel_asce();
tmp1 = -256UL;
asm volatile(
" sacf 0\n"
Expand Down Expand Up @@ -225,7 +225,7 @@ static inline unsigned long copy_in_user_mvc(void __user *to, const void __user
{
unsigned long tmp1;

update_primary_asce(current);
load_kernel_asce();
asm volatile(
" sacf 256\n"
" "AHI" %0,-1\n"
Expand Down Expand Up @@ -292,7 +292,7 @@ static inline unsigned long clear_user_xc(void __user *to, unsigned long size)
{
unsigned long tmp1, tmp2;

update_primary_asce(current);
load_kernel_asce();
asm volatile(
" sacf 256\n"
" "AHI" %0,-1\n"
Expand Down Expand Up @@ -358,7 +358,7 @@ unsigned long __strnlen_user(const char __user *src, unsigned long size)
{
if (unlikely(!size))
return 0;
update_primary_asce(current);
load_kernel_asce();
return strnlen_user_srst(src, size);
}
EXPORT_SYMBOL(__strnlen_user);
Expand Down
10 changes: 6 additions & 4 deletions arch/s390/mm/pgtable.c
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Original file line number Diff line number Diff line change
Expand Up @@ -53,8 +53,10 @@ static void __crst_table_upgrade(void *arg)
{
struct mm_struct *mm = arg;

if (current->active_mm == mm)
update_user_asce(mm, 1);
if (current->active_mm == mm) {
clear_user_asce();
set_user_asce(mm);
}
__tlb_flush_local();
}

Expand Down Expand Up @@ -108,7 +110,7 @@ void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
pgd_t *pgd;

if (current->active_mm == mm) {
clear_user_asce(mm, 1);
clear_user_asce();
__tlb_flush_mm(mm);
}
while (mm->context.asce_limit > limit) {
Expand All @@ -134,7 +136,7 @@ void crst_table_downgrade(struct mm_struct *mm, unsigned long limit)
crst_table_free(mm, (unsigned long *) pgd);
}
if (current->active_mm == mm)
update_user_asce(mm, 1);
set_user_asce(mm);
}
#endif

Expand Down

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