Re: [RFC PATCH 4/6] x86/mm/tlb: Refactor common code into flush_tlb_on_cpus()

[Peter Zijlstra]

On Sat, May 25, 2019 at 01:22:01AM -0700, Nadav Amit wrote:

> 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.

> @@ -786,18 +804,9 @@ 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();
> -     }
> -
> -     if (cpumask_any_but(mm_cpumask(mm), cpu) < nr_cpu_ids)
> -             flush_tlb_others(mm_cpumask(mm), info);

So if we want to double check that; we'd add:

        WARN_ON_ONCE(cpumask_test_cpu(smp_processor_id(), mm_cpumask(mm)) ==
                     (mm == this_cpu_read(cpu_tlbstate.loaded_mm)));

right?

> +     flush_tlb_on_cpus(mm_cpumask(mm), info);
>  
>       put_flush_tlb_info();
> -     put_cpu();
>  }