Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> wrote:
> On 06/14/2016 09:47 AM, Nadav Amit wrote:
>> Lukasz Anaczkowski <lukasz.anaczkowski@xxxxxxxxx> wrote:
>>
>>>> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>>>> +void fix_pte_leak(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
>>>> +{
>> Here there should be a call to smp_mb__after_atomic() to synchronize with
>> switch_mm. I submitted a similar patch, which is still pending (hint).
>>
>>>> + if (cpumask_any_but(mm_cpumask(mm), smp_processor_id()) < nr_cpu_ids) {
>>>> + trace_tlb_flush(TLB_LOCAL_SHOOTDOWN, TLB_FLUSH_ALL);
>>>> + flush_tlb_others(mm_cpumask(mm), mm, addr,
>>>> + addr + PAGE_SIZE);
>>>> + mb();
>>>> + set_pte(ptep, __pte(0));
>>>> + }
>>>> +}
>
> Shouldn't that barrier be incorporated in the TLB flush code itself and
> not every single caller (like this code is)?
>
> It is insane to require individual TLB flushers to be concerned with the
> barriers.
IMHO it is best to use existing flushing interfaces instead of creating
new ones.
In theory, fix_pte_leak could have used flush_tlb_page. But the problem
is that flush_tlb_page requires the vm_area_struct as an argument, which
ptep_get_and_clear (and others) do not have.
I don’t know which architecture needs the vm_area_struct, since x86 and
some others I looked at (e.g., ARM) only need the mm_struct.
Nadav
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