Re: [PATCH v4 01/12] powerpc/64s: Do not re-activate batched TLB flush

[Kevin Brodsky <kevin.brodsky@xxxxxxx>]

On 05/11/2025 02:46, Ritesh Harjani (IBM) wrote:
> Kevin Brodsky <kevin.brodsky@xxxxxxx> writes:
>
>> From: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
>>
>> Since commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash
>> lazy mmu mode") a task can not be preempted while in lazy MMU mode.
>> Therefore, the batch re-activation code is never called, so remove it.
>>
>> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
>> Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
>> ---
>>  arch/powerpc/include/asm/thread_info.h |  2 --
>>  arch/powerpc/kernel/process.c          | 25 -------------------------
>>  2 files changed, 27 deletions(-)
>>
> Since the commit referenced in above disables the preemption in
> arch_enter_lazy_mmu(), so the expectation is that we will never be
> context switched while in lazy_mmu, hence the code changes in
> switch_to() around __flush_tlb_pending() should ideally never be called.

Correct, that's the idea.

> With this analysis - the patch looks good to me. I will give this entire
> patch series a try on Power HW with Hash mmu too (which uses lazy mmu and
> let you know the results of that)!

That'd be very appreciated, thanks a lot!

> For this patch please feel free to add:
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@xxxxxxxxx>
>
>
> CC: Venkat who also runs CI on linux Power HW for upstream testing :)

Ack, will Cc you both in the next version.

- Kevin