Re: [PATCH] perf/events: Replace READ_ONCE() with standard pgtable accessors

[Anshuman Khandual]

On 07/04/26 12:48 PM, Peter Zijlstra wrote:
> On Tue, Apr 07, 2026 at 08:48:22AM +0200, David Hildenbrand (Arm) wrote:
>> On 4/7/26 05:28, Anshuman Khandual wrote:
>>>
>>>
>>> On 27/02/26 11:57 AM, Anshuman Khandual wrote:
>>>> Replace raw READ_ONCE() dereferences of pgtable entries with corresponding
>>>> standard page table accessors pxdp_get() in perf_get_pgtable_size(). These
>>>> accessors default to READ_ONCE() on platforms that don't override them. So
>>>> there is no functional change on such platforms.
>>>>
>>>> However arm64 platform is being extended to support 128 bit page tables via
>>>> a new architecture feature i.e FEAT_D128 in which case READ_ONCE() will not
>>>> provide required single copy atomic access for 128 bit page table entries.
>>>> Although pxdp_get() accessors can later be overridden on arm64 platform to
>>>> extend required single copy atomicity support on 128 bit entries.
>>>>
>>>> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
>>>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>>>> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>>>> Cc: Ingo Molnar <mingo@xxxxxxxxxx>
>>>> Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
>>>> Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
>>>> Cc: linux-perf-users@xxxxxxxxxxxxxxx
>>>> Cc: linux-mm@xxxxxxxxx
>>>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>>>> Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
>>>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>>>> ---
>>>> This patch applies both on v7.0-rc1 and mm-unstable.
>>>>
>>>> Part of the D128 series but independent. Hence could be considered on its own.
>>>>
>>>> https://lore.kernel.org/all/20260224051153.3150613-5-anshuman.khandual@xxxxxxx/
>>>>
>>>> Collected Peter's tag from an off list conversation.
>>>
>>> Gentle ping. 
>>>
>>> Still don't see this patch in latest next-20260406. Hence just
>>> wondering which tree and branch this patch is being picked up ?
>>
>> It's a trivial change and the last generic code change required for you
>> arm64 D128 change, right?
>>
>> I would assume this to go through the tip tree, but if Peter agrees we
>> could route this (mm) patch through the MM tree.
> 
> Right, I thought this was part of a larger series and figured it would
> ride along with whatever other patches.
> 
> If you still want me to pick this up, I can, just state clearly where
> this ought to go.

It would be great if you could pick this up. Thanks !