[PATCH v2] powerpc/npu: Cleanup MMIO ATSD flushing

[Balbir Singh]

On Wed, Feb 28, 2018 at 9:50 PM, Michael Ellerman <mpe at ellerman.id.au> wrote:
> Alistair Popple <alistair at popple.id.au> writes:
>
>>> @aneesh can you please look at this? @mpe can we pick this up if there
>>> are no objections?
>>
>> @mpe any objections to picking this up for this release? Or do you want to wait
>> for the next one? (there are likely more bugfixes coming for ATS support).
>
> I can grab it for this release if it's fixing a bug, the subject makes
> it sound like a cleanup. Do we have a Fixes tag for it?
>
> I don't particularly like the potentially very long loop in
> pnv_npu2_invalidate_helper() which spends most of its time with
> interrupts off. I worry we're going to see soft lockups pointing there
> if we get a very large invalidate.
>
We have the same loop today in pnv_npu2_mn_invalidate_range(). The bug
fix is really the fix to invalidate the right page size. I agree we
can optimize this better, in fact if the mmu notifier is made blocking
then we can even do cond_resched(). I however agree, the right thing
to do is to figure out the right trade-off of invalidate range size to
flushing the entire PID

Balbir Singh.