linux-kernel - Re: [PATCH 6/6] powerpc/64s: Do not re-activate batched TLB flush

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Message-ID: <4001ebcc-7516-4bea-a920-8750f029b442@arm.com>
Date: Tue, 7 Oct 2025 16:33:42 +0200
From: Kevin Brodsky <kevin.brodsky@....com>
To: "Ritesh Harjani (IBM)" <ritesh.list@...il.com>,
 Alexander Gordeev <agordeev@...ux.ibm.com>,
 Madhavan Srinivasan <maddy@...ux.ibm.com>,
 Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin <npiggin@...il.com>
Cc: linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 6/6] powerpc/64s: Do not re-activate batched TLB flush

On 07/10/2025 11:40, Ritesh Harjani (IBM) wrote:
> Kevin Brodsky <kevin.brodsky@....com> writes:
>
>> On 17/06/2025 17:11, Alexander Gordeev wrote:
>>> On Thu, Jun 12, 2025 at 07:36:13PM +0200, Alexander Gordeev wrote:
>>>> 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@...ux.ibm.com>
>>>> ---
>>>>  arch/powerpc/include/asm/thread_info.h |  2 --
>>>>  arch/powerpc/kernel/process.c          | 25 -------------------------
>>>>  2 files changed, 27 deletions(-)
>>> Hi All,
>>>
>>> (I trimmed non-ppc mailing lists/people).
>>>
>>> The whole series does not seem to make it, but this patch alone is still
>>> applicable and makes sence, if I am not mistaken.
>> Yes, I agree. I arrived at the same conclusion working on the next
>> version of the nested lazy_mmu series [1].
>> [1]
>> https://lore.kernel.org/all/20250908073931.4159362-1-kevin.brodsky@arm.com/
> Yes, we disable preemption while in lazy mmu mode for Hash, so I agree that
> we won't call into __switch_to() in between preempt_disable()/_enable().
> So it does look like that we don't need that code.

Thanks for confirming.

>> May I include this patch in v3?
>>
> That should be ok.

Thanks!

- Kevin