Subject: Re: [PATCH v3] powerpc: Fix PTE page address mismatch in pgtable ctor/dtor

From: Benjamin Herrenschmidt <[email-masked]>
Date: Sun, 08 Dec 2013 07:27:59 +1100

On Sat, 2013-12-07 at 09:06 -0500, Hong H. Pham wrote:

> diff --git a/arch/powerpc/include/asm/pgalloc-32.h b/arch/powerpc/include/asm/pgalloc-32.h
> index 27b2386..842846c 100644
> --- a/arch/powerpc/include/asm/pgalloc-32.h
> +++ b/arch/powerpc/include/asm/pgalloc-32.h
> @@ -84,10 +84,8 @@ static inline void pgtable_free_tlb(struct mmu_gather *tlb,
>  static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t table,
>  				  unsigned long address)
>  {
> -	struct page *page = page_address(table);
> -
>  	tlb_flush_pgtable(tlb, address);
> -	pgtable_page_dtor(page);
> -	pgtable_free_tlb(tlb, page, 0);
> +	pgtable_page_dtor(table);
> +	pgtable_free_tlb(tlb, page_address(table), 0);
>  }

Ok so your description of the problem confused me a bit, but I see that
in the !64K page, pgtable_t is already a struct page so yes, the
page_address() call here is bogus.

However, I also noticed that in the 64k page case, we don't call the dto
at all. Is that a problem ?

Also, Aneesh, shouldn't we just fix the disconnect here and have
pgtable_t always be the same type ? The way this is now is confusing
and error prone...

>  #endif /* _ASM_POWERPC_PGALLOC_32_H */
> diff --git a/arch/powerpc/include/asm/pgalloc-64.h b/arch/powerpc/include/asm/pgalloc-64.h
> index f65e27b..256d6f8 100644
> --- a/arch/powerpc/include/asm/pgalloc-64.h
> +++ b/arch/powerpc/include/asm/pgalloc-64.h
> @@ -144,11 +144,9 @@ static inline void pgtable_free_tlb(struct mmu_gather *tlb,
>  static inline void __pte_free_tlb(struct mmu_gather *tlb, pgtable_t table,
>  				  unsigned long address)
>  {
> -	struct page *page = page_address(table);
> -
>  	tlb_flush_pgtable(tlb, address);
> -	pgtable_page_dtor(page);
> -	pgtable_free_tlb(tlb, page, 0);
> +	pgtable_page_dtor(table);
> +	pgtable_free_tlb(tlb, page_address(table), 0);
>  }
>  
>  #else /* if CONFIG_PPC_64K_PAGES */

Ben.