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s390/mm: simplify the TLB flushing code

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ptep_flush_lazy and pmdp_flush_lazy use mm->context.attach_count to
decide between a lazy TLB flush vs an immediate TLB flush. The field
contains two 16-bit counters, the number of CPUs that have the mm
attached and can create TLB entries for it and the number of CPUs in
the middle of a page table update.

The __tlb_flush_asce, ptep_flush_direct and pmdp_flush_direct functions
use the attach counter and a mask check with mm_cpumask(mm) to decide
between a local flush local of the current CPU and a global flush.

For all these functions the decision between lazy vs immediate and
local vs global TLB flush can be based on CPU masks. There are two
masks:  the mm->context.cpu_attach_mask with the CPUs that are actively
using the mm, and the mm_cpumask(mm) with the CPUs that have used the
mm since the last full flush. The decision between lazy vs immediate
flush is based on the mm->context.cpu_attach_mask, to decide between
local vs global flush the mm_cpumask(mm) is used.

With this patch all checks will use the CPU masks, the old counter
mm->context.attach_count with its two 16-bit values is turned into a
single counter mm->context.flush_count that keeps track of the number
of CPUs with incomplete page table updates. The sole user of this
counter is finish_arch_post_lock_switch() which waits for the end of
all page table updates.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Martin Schwidefsky
2016-05-25 09:45:26 +02:00
parent 7dd968163f
commit 64f31d5802
6 changed files with 28 additions and 48 deletions
Download Patch File Download Diff File Expand all files Collapse all files

34
arch/s390/mm/pgtable.c
View File

@@ -27,40 +27,37 @@
static inline pte_t ptep_flush_direct(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
int active, count;
pte_t old;
old = *ptep;
if (unlikely(pte_val(old) & _PAGE_INVALID))
return old;
active = (mm == current->active_mm) ? 1 : 0;
count = atomic_add_return(0x10000, &mm->context.attach_count);
if (MACHINE_HAS_TLB_LC && (count & 0xffff) <= active &&
atomic_inc(&mm->context.flush_count);
if (MACHINE_HAS_TLB_LC &&
cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id())))
__ptep_ipte_local(addr, ptep);
else
__ptep_ipte(addr, ptep);
atomic_sub(0x10000, &mm->context.attach_count);
atomic_dec(&mm->context.flush_count);
return old;
}
static inline pte_t ptep_flush_lazy(struct mm_struct *mm,
unsigned long addr, pte_t *ptep)
{
int active, count;
pte_t old;
old = *ptep;
if (unlikely(pte_val(old) & _PAGE_INVALID))
return old;
active = (mm == current->active_mm) ? 1 : 0;
count = atomic_add_return(0x10000, &mm->context.attach_count);
if ((count & 0xffff) <= active) {
atomic_inc(&mm->context.flush_count);
if (cpumask_equal(&mm->context.cpu_attach_mask,
cpumask_of(smp_processor_id()))) {
pte_val(*ptep) |= _PAGE_INVALID;
mm->context.flush_mm = 1;
} else
__ptep_ipte(addr, ptep);
atomic_sub(0x10000, &mm->context.attach_count);
atomic_dec(&mm->context.flush_count);
return old;
}
@@ -289,7 +286,6 @@ EXPORT_SYMBOL(ptep_modify_prot_commit);
static inline pmd_t pmdp_flush_direct(struct mm_struct *mm,
unsigned long addr, pmd_t *pmdp)
{
int active, count;
pmd_t old;
old = *pmdp;
@@ -299,36 +295,34 @@ static inline pmd_t pmdp_flush_direct(struct mm_struct *mm,
__pmdp_csp(pmdp);
return old;
}
active = (mm == current->active_mm) ? 1 : 0;
count = atomic_add_return(0x10000, &mm->context.attach_count);
if (MACHINE_HAS_TLB_LC && (count & 0xffff) <= active &&
atomic_inc(&mm->context.flush_count);
if (MACHINE_HAS_TLB_LC &&
cpumask_equal(mm_cpumask(mm), cpumask_of(smp_processor_id())))
__pmdp_idte_local(addr, pmdp);
else
__pmdp_idte(addr, pmdp);
atomic_sub(0x10000, &mm->context.attach_count);
atomic_dec(&mm->context.flush_count);
return old;
}
static inline pmd_t pmdp_flush_lazy(struct mm_struct *mm,
unsigned long addr, pmd_t *pmdp)
{
int active, count;
pmd_t old;
old = *pmdp;
if (pmd_val(old) & _SEGMENT_ENTRY_INVALID)
return old;
active = (mm == current->active_mm) ? 1 : 0;
count = atomic_add_return(0x10000, &mm->context.attach_count);
if ((count & 0xffff) <= active) {
atomic_inc(&mm->context.flush_count);
if (cpumask_equal(&mm->context.cpu_attach_mask,
cpumask_of(smp_processor_id()))) {
pmd_val(*pmdp) |= _SEGMENT_ENTRY_INVALID;
mm->context.flush_mm = 1;
} else if (MACHINE_HAS_IDTE)
__pmdp_idte(addr, pmdp);
else
__pmdp_csp(pmdp);
atomic_sub(0x10000, &mm->context.attach_count);
atomic_dec(&mm->context.flush_count);
return old;
}