linux-kernel - Re: [PATCH 1/3] mm: set page fault address for update_mmu_cache

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Date:   Wed, 24 Jun 2020 12:49:42 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Bibo Mao <maobibo@...ngson.cn>
Cc:     Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Daniel Silsby <dansilsby@...il.com>,
        linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [PATCH 1/3] mm: set page fault address for update_mmu_cache_pmd

On Wed, 24 Jun 2020 17:26:30 +0800 Bibo Mao <maobibo@...ngson.cn> wrote:

> update_mmu_cache_pmd is used to update tlb for the pmd entry by
> software. On MIPS system, the tlb entry indexed by page fault
> address maybe exists already, only that tlb entry may be small
> page, also it may be huge page. Before updating pmd entry with
> huge page size, older tlb entry need to be invalidated.
> 
> Here page fault address is passed to function update_mmu_cache_pmd,
> rather than pmd huge page start address. The page fault address
> can be used for invalidating older tlb entry.
> 
> ...
>
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -554,11 +554,20 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
>  #define	__HAVE_ARCH_UPDATE_MMU_TLB
>  #define update_mmu_tlb	update_mmu_cache
>  
> +extern void local_flush_tlb_page(struct vm_area_struct *vma,
> +				unsigned long page);

This is unfortunate.  We can't #include <asm/'tlbflush.h>?

>  static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
>  	unsigned long address, pmd_t *pmdp)
>  {
>  	pte_t pte = *(pte_t *)pmdp;
>  
> +	/*
> +	 * If pmd_none is true, older tlb entry will be normal page.
> +	 * here to invalidate older tlb entry indexed by address
> +	 * parameter address must be page fault address rather than
> +	 * start address of pmd huge page
> +	 */
> +	local_flush_tlb_page(vma, address);
>  	__update_tlb(vma, address, pte);
>  }
>