[RFC 01/10] x86/mm: Reimplement flush_tlb_page() using flush_tlb_mm_range()

Andy Lutomirski
2017-05-07T22:06:29Z

flush_tlb_page() was very similar to flush_tlb_mm_range() except that
it had a couple of issues:

- It was missing an smp_mb() in the case where
current->active_mm != mm. (This is a longstanding bug reported by
Nadav Amit.)

- It was missing tracepoints and vm counter updates.

The only reason that I can see for keeping it at as a separate
function is that it could avoid a few branches that
flush_tlb_mm_range() needs to decide to flush just one page. This
hardly seems worthwhile. If we decide we want to get rid of those
branches again, a better way would be to introduce an
__flush_tlb_mm_range() helper and make both flush_tlb_page() and
flush_tlb_mm_range() use it.

Cc: Rik van Riel <riel@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Nadav Amit <namit@vmware.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
---
arch/x86/include/asm/tlbflush.h | 6 +++++-
arch/x86/mm/tlb.c | 27 ---------------------------
2 files changed, 5 insertions(+), 28 deletions(-)

diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h
index 6ed9ea469b48..5ed64cdaf536 100644
--- a/arch/x86/include/asm/tlbflush.h
+++ b/arch/x86/include/asm/tlbflush.h
@@ -307,11 +307,15 @@ static inline void flush_tlb_kernel_range(unsigned long start,
flush_tlb_mm_range(vma->vm_mm, start, end, vma->vm_flags)

extern void flush_tlb_all(void);
-extern void flush_tlb_page(struct vm_area_struct *, unsigned long);
extern void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
unsigned long end, unsigned long vmflag);
extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);

+static inline void flush_tlb_page(struct vm_area_struct *vma, unsigned long a)
+{
+ flush_tlb_mm_range(vma->vm_mm, a, a + PAGE_SIZE, 0);
+}
+
void native_flush_tlb_others(const struct cpumask *cpumask,
struct mm_struct *mm,
unsigned long start, unsigned long end);
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 6e7bedf69af7..fe6471132ea3 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -354,33 +354,6 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
preempt_enable();
}

-void flush_tlb_page(struct vm_area_struct *vma, unsigned long start)
-{
- struct mm_struct *mm = vma->vm_mm;
-
- preempt_disable();
-
- if (current->active_mm == mm) {
- if (current->mm) {
- /*
- * Implicit full barrier (INVLPG) that synchronizes
- * with switch_mm.
- */
- __flush_tlb_one(start);
- } else {
- leave_mm(smp_processor_id());
-
- /* Synchronize with switch_mm. */
- smp_mb();
- }
- }
-
- if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids)
- flush_tlb_others(mm_cpumask(mm), mm, start, start + PAGE_SIZE);
-
- preempt_enable();
-}
-
static void do_flush_tlb_all(void *info)
{
count_vm_tlb_event(NR_TLB_REMOTE_FLUSH_RECEIVED);
--
2.9.3