Re: [PATCH 3/3] powerpc/8xx: Provide ptep_get() with 16k pages

[Peter Zijlstra]

On Mon, Jun 15, 2020 at 12:57:59PM +0000, Christophe Leroy wrote:
> READ_ONCE() now enforces atomic read, which leads to:


> Fixes: 2ab3a0a02905 ("READ_ONCE: Enforce atomicity for {READ,WRITE}_ONCE() memory accesses")
> Cc: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
> ---
>  arch/powerpc/include/asm/nohash/32/pgtable.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/arch/powerpc/include/asm/nohash/32/pgtable.h b/arch/powerpc/include/asm/nohash/32/pgtable.h
> index b56f14160ae5..77addb599ce7 100644
> --- a/arch/powerpc/include/asm/nohash/32/pgtable.h
> +++ b/arch/powerpc/include/asm/nohash/32/pgtable.h
> @@ -286,6 +286,16 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm, unsigned long addr,
>  	return __pte(pte_update(mm, addr, ptep, ~0, 0, 0));
>  }
>  
> +#if defined(CONFIG_PPC_8xx) && defined(CONFIG_PPC_16K_PAGES)
> +#define __HAVE_ARCH_PTEP_GET
> +static inline pte_t ptep_get(pte_t *ptep)
> +{
> +	pte_t pte = {READ_ONCE(ptep->pte), 0, 0, 0};
> +
> +	return pte;
> +}
> +#endif

Would it make sense to have a comment with this magic? The casual reader
might wonder WTH just happened when he stumbles on this :-)

Other than that, the series looks good to me, Thanks!

Acked-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>