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

[Anshuman Khandual]

On 08/04/26 6:19 PM, David Laight wrote:
> On Tue, 7 Apr 2026 08:58:46 +0530
> Anshuman Khandual <anshuman.khandual@xxxxxxx> 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.
>>
> 
> Did you consider enhancing READ_ONCE() to support 128bit accesses on arm64?

Yes although it does not really meet all requirements for 128 bit page table access.