linux-kernel - Re: [PATCH 05/15] csky: switch to generic version of pte allocation

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Date:   Sat, 4 May 2019 00:03:48 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greentime Hu <green.hu@...il.com>,
        Guan Xuetao <gxt@....edu.cn>, Helge Deller <deller@....de>,
        Ley Foon Tan <lftan@...era.com>,
        Matthew Wilcox <willy@...radead.org>,
        Matt Turner <mattst88@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Michal Hocko <mhocko@...e.com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Burton <paul.burton@...s.com>,
        Richard Kuo <rkuo@...eaurora.org>,
        Richard Weinberger <richard@....at>,
        Russell King <linux@...linux.org.uk>,
        Sam Creasey <sammy@...my.net>, x86@...nel.org,
        linux-alpha@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-hexagon@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-m68k@...ts.linux-m68k.org, linux-mips@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
        linux-riscv@...ts.infradead.org, linux-um@...ts.infradead.org,
        nios2-dev@...ts.rocketboards.org
Subject: Re: [PATCH 05/15] csky: switch to generic version of pte allocation

Hi Mike,

Acked-by: Guo Ren <ren_guo@...ky.com>

On Thu, May 02, 2019 at 06:28:32PM +0300, Mike Rapoport wrote:
> The csky implementation pte_alloc_one(), pte_free_kernel() and pte_free()
> is identical to the generic except of lack of __GFP_ACCOUNT for the user
> PTEs allocation.
> 
> Switch csky to use generic version of these functions.
Ok.

> 
> The csky implementation of pte_alloc_one_kernel() is not replaced because
> it does not clear the allocated page but rather sets each PTE in it to a
> non-zero value.
Yes, we must set each PTE to _PAGE_GLOBAL because hardware refill the
MMU TLB entry with two PTEs and it use the result of pte0.global | pte1.global.
If pte0 is valid and pte1 is invalid, we must set _PAGE_GLOBAL in
invalid pte entry. Fortunately, there is no performance issue.

> 
> The pte_free_kernel() and pte_free() versions on csky are identical to the
> generic ones and can be simply dropped.
Ok.

Best Regards
 Guo Ren

> 
> Signed-off-by: Mike Rapoport <rppt@...ux.ibm.com>
> ---
>  arch/csky/include/asm/pgalloc.h | 30 +++---------------------------
>  1 file changed, 3 insertions(+), 27 deletions(-)
> 
> diff --git a/arch/csky/include/asm/pgalloc.h b/arch/csky/include/asm/pgalloc.h
> index d213bb4..98c571670 100644
> --- a/arch/csky/include/asm/pgalloc.h
> +++ b/arch/csky/include/asm/pgalloc.h
> @@ -8,6 +8,9 @@
>  #include <linux/mm.h>
>  #include <linux/sched.h>
>  
> +#define __HAVE_ARCH_PTE_ALLOC_ONE_KERNEL
> +#include <asm-generic/pgalloc.h>	/* for pte_{alloc,free}_one */
> +
>  static inline void pmd_populate_kernel(struct mm_struct *mm, pmd_t *pmd,
>  					pte_t *pte)
>  {
> @@ -39,33 +42,6 @@ static inline pte_t *pte_alloc_one_kernel(struct mm_struct *mm)
>  	return pte;
>  }
>  
> -static inline struct page *pte_alloc_one(struct mm_struct *mm)
> -{
> -	struct page *pte;
> -
> -	pte = alloc_pages(GFP_KERNEL | __GFP_ZERO, 0);
> -	if (!pte)
> -		return NULL;
> -
> -	if (!pgtable_page_ctor(pte)) {
> -		__free_page(pte);
> -		return NULL;
> -	}
> -
> -	return pte;
> -}
> -
> -static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
> -{
> -	free_pages((unsigned long)pte, PTE_ORDER);
> -}
> -
> -static inline void pte_free(struct mm_struct *mm, pgtable_t pte)
> -{
> -	pgtable_page_dtor(pte);
> -	__free_pages(pte, PTE_ORDER);
> -}
> -
>  static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
>  {
>  	free_pages((unsigned long)pgd, PGD_ORDER);
> -- 
> 2.7.4
>