[PATCH 3/9] x86/mm/tlb: Refactor common code into flush_tlb_on_cpus()

[Nadav Amit]

arch_tlbbatch_flush() and flush_tlb_mm_range() have very similar code,
which is effectively the same. Extract the mutual code into a new
function flush_tlb_on_cpus().

There is one functional change, which should not affect correctness:
flush_tlb_mm_range compared loaded_mm and the mm to figure out if local
flush is needed. Instead, the common code would look at the mm_cpumask()
which should give the same result. Performance should not be affected,
since this cpumask should not change in such a frequency that would
introduce cache contention.

Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: Andy Lutomirski <l...@kernel.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Signed-off-by: Nadav Amit <na...@vmware.com>
---
 arch/x86/mm/tlb.c | 62 ++++++++++++++++++++++++++---------------------
 1 file changed, 34 insertions(+), 28 deletions(-)

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 91f6db92554c..c34bcf03f06f 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -734,7 +734,11 @@ static inline struct flush_tlb_info 
*get_flush_tlb_info(struct mm_struct *mm,
                        unsigned int stride_shift, bool freed_tables,
                        u64 new_tlb_gen)
 {
-       struct flush_tlb_info *info = this_cpu_ptr(&flush_tlb_info);
+       struct flush_tlb_info *info;
+
+       preempt_disable();
+
+       info = this_cpu_ptr(&flush_tlb_info);
 
 #ifdef CONFIG_DEBUG_VM
        /*
@@ -762,6 +766,23 @@ static inline void put_flush_tlb_info(void)
        barrier();
        this_cpu_dec(flush_tlb_info_idx);
 #endif
+       preempt_enable();
+}
+
+static void flush_tlb_on_cpus(const cpumask_t *cpumask,
+                             const struct flush_tlb_info *info)
+{
+       int this_cpu = smp_processor_id();
+
+       if (cpumask_test_cpu(this_cpu, cpumask)) {
+               lockdep_assert_irqs_enabled();
+               local_irq_disable();
+               flush_tlb_func_local(info, TLB_LOCAL_MM_SHOOTDOWN);
+               local_irq_enable();
+       }
+
+       if (cpumask_any_but(cpumask, this_cpu) < nr_cpu_ids)
+               flush_tlb_others(cpumask, info);
 }
 
 void flush_tlb_mm_range(struct mm_struct *mm, unsigned long start,
@@ -770,9 +791,6 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned long 
start,
 {
        struct flush_tlb_info *info;
        u64 new_tlb_gen;
-       int cpu;
-
-       cpu = get_cpu();
 
        /* Should we flush just the requested range? */
        if ((end == TLB_FLUSH_ALL) ||
@@ -787,18 +805,18 @@ void flush_tlb_mm_range(struct mm_struct *mm, unsigned 
long start,
        info = get_flush_tlb_info(mm, start, end, stride_shift, freed_tables,
                                  new_tlb_gen);
 
-       if (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) {
-               lockdep_assert_irqs_enabled();
-               local_irq_disable();
-               flush_tlb_func_local(info, TLB_LOCAL_MM_SHOOTDOWN);
-               local_irq_enable();
-       }
+       /*
+        * Assert that mm_cpumask() corresponds with the loaded mm. We got one
+        * exception: for init_mm we do not need to flush anything, and the
+        * cpumask does not correspond with loaded_mm.
+        */
+       VM_WARN_ON_ONCE(cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm)) !=
+                       (mm == this_cpu_read(cpu_tlbstate.loaded_mm)) &&
+                       mm != &init_mm);
 
-       if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
-               flush_tlb_others(mm_cpumask(mm), info);
+       flush_tlb_on_cpus(mm_cpumask(mm), info);
 
        put_flush_tlb_info();
-       put_cpu();
 }
 
 
@@ -833,13 +851,11 @@ void flush_tlb_kernel_range(unsigned long start, unsigned 
long end)
        } else {
                struct flush_tlb_info *info;
 
-               preempt_disable();
                info = get_flush_tlb_info(NULL, start, end, 0, false, 0);
 
                on_each_cpu(do_kernel_range_flush, info, 1);
 
                put_flush_tlb_info();
-               preempt_enable();
        }
 }
 
@@ -857,21 +873,11 @@ static const struct flush_tlb_info full_flush_tlb_info = {
 
 void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
 {
-       int cpu = get_cpu();
-
-       if (cpumask_test_cpu(cpu, &batch->cpumask)) {
-               lockdep_assert_irqs_enabled();
-               local_irq_disable();
-               flush_tlb_func_local(&full_flush_tlb_info, TLB_LOCAL_SHOOTDOWN);
-               local_irq_enable();
-       }
-
-       if (cpumask_any_but(&batch->cpumask, cpu) < nr_cpu_ids)
-               flush_tlb_others(&batch->cpumask, &full_flush_tlb_info);
+       preempt_disable();
+       flush_tlb_on_cpus(&batch->cpumask, &full_flush_tlb_info);
+       preempt_enable();
 
        cpumask_clear(&batch->cpumask);
-
-       put_cpu();
 }
 
 static ssize_t tlbflush_read_file(struct file *file, char __user *user_buf,
-- 
2.20.1