Re: [PATCH V2 02/14] arm64/mm: Route all pgtable reads via ptval_get()

[Anshuman Khandual]

On Wed, Sep 16, 2026 at 03:38:13PM +0200, David Hildenbrand (Arm) wrote:
> On 9/7/26 05:50, Anshuman Khandual wrote:
> > Define arm64 platform specific implementations for new pxdp_get() helpers.
> > These resolve into READ_ONCE(), thus ensuring required single copy atomic
> > semantics for the page table entry reads.
> > 
> > In future this infrastructure can be used for D128 to maintain single copy
> > atomicity semantics with inline asm blocks.
> > 
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Will Deacon <will@xxxxxxxxxx>
> > Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > ---
> >  arch/arm64/include/asm/pgtable.h | 38 +++++++++++++++++++++++++++-----
> >  1 file changed, 32 insertions(+), 6 deletions(-)
> > 
> > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> > index 83087b70f192..f764132ca34e 100644
> > --- a/arch/arm64/include/asm/pgtable.h
> > +++ b/arch/arm64/include/asm/pgtable.h
> > @@ -84,6 +84,32 @@ static inline void arch_leave_lazy_mmu_mode(void)
> >  	arch_flush_lazy_mmu_mode();
> >  }
> >  
> > +#define ptval_get(x)		READ_ONCE(x)
> > +
> > +#define pmdp_get pmdp_get
> > +static inline pmd_t pmdp_get(pmd_t *pmdp)
> > +{
> > +	return ptval_get(*pmdp);
> > +}
> Ah, one thing: you could pass a const pointer to all these read helpers.

Sure but first will have to change their defaults in include/linux/pgtable.h

> 
> -- 
> Cheers,
> 
> David