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

[Anshuman Khandual <anshuman.khandual@arm.com>]

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@linux-foundation.org>
> Cc: David Hildenbrand <david@kernel.org>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
> Cc: Namhyung Kim <namhyung@kernel.org>
> Cc: linux-perf-users@vger.kernel.org
> Cc: linux-mm@kvack.org
> Cc: linux-kernel@vger.kernel.org
> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> 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@arm.com/
> 
> 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 ?

Thank you

- Anshuman
  
> 
>  kernel/events/core.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/events/core.c b/kernel/events/core.c
> index ac70d68217b6..4ee151cd2c6d 100644
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -8422,7 +8422,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
>  	pte_t *ptep, pte;
>  
>  	pgdp = pgd_offset(mm, addr);
> -	pgd = READ_ONCE(*pgdp);
> +	pgd = pgdp_get(pgdp);
>  	if (pgd_none(pgd))
>  		return 0;
>  
> @@ -8430,7 +8430,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
>  		return pgd_leaf_size(pgd);
>  
>  	p4dp = p4d_offset_lockless(pgdp, pgd, addr);
> -	p4d = READ_ONCE(*p4dp);
> +	p4d = p4dp_get(p4dp);
>  	if (!p4d_present(p4d))
>  		return 0;
>  
> @@ -8438,7 +8438,7 @@ static u64 perf_get_pgtable_size(struct mm_struct *mm, unsigned long addr)
>  		return p4d_leaf_size(p4d);
>  
>  	pudp = pud_offset_lockless(p4dp, p4d, addr);
> -	pud = READ_ONCE(*pudp);
> +	pud = pudp_get(pudp);
>  	if (!pud_present(pud))
>  		return 0;
>