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

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Message-ID: <20190503161808.GA11596@guoren-Inspiron-7460>
Date:   Sat, 4 May 2019 00:18:08 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Michal Hocko <mhocko@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Palmer Dabbelt <palmer@...ive.com>, linux-mips@...r.kernel.org,
        Michael Ellerman <mpe@...erman.id.au>,
        linux-hexagon@...r.kernel.org, linux-riscv@...ts.infradead.org,
        linux-arch@...r.kernel.org, Richard Weinberger <richard@....at>,
        Helge Deller <deller@....de>, x86@...nel.org,
        Russell King <linux@...linux.org.uk>,
        Matthew Wilcox <willy@...radead.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Matt Turner <mattst88@...il.com>,
        Sam Creasey <sammy@...my.net>, Arnd Bergmann <arnd@...db.de>,
        linux-um@...ts.infradead.org, linux-m68k@...ts.linux-m68k.org,
        Greentime Hu <green.hu@...il.com>,
        nios2-dev@...ts.rocketboards.org, Guan Xuetao <gxt@....edu.cn>,
        linux-arm-kernel@...ts.infradead.org, linux-parisc@...r.kernel.org,
        linux-kernel@...r.kernel.org, Richard Kuo <rkuo@...eaurora.org>,
        Paul Burton <paul.burton@...s.com>,
        linux-alpha@...r.kernel.org, Ley Foon Tan <lftan@...era.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH 05/15] csky: switch to generic version of pte allocation

On Sat, May 04, 2019 at 12:03:48AM +0800, Guo Ren wrote:
> 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.
                                                       ^^^^^^^^^^^^^^^^^^^^^^^^^
                                              correct: 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
> > 
> 
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> linux-riscv@...ts.infradead.org
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