Re: [PATCH V3] MIPS: make userspace mapping young by default

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On Sat, Sep 19, 2020 at 03:47:31PM +0800, Huang Pei wrote:

Ping?
> MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
> the second TLB Invalid exception is just triggered by __update_tlb from
> do_page_fault writing tlb without _PAGE_VALID set. With this patch, it
> only take 1 TLB Miss + 1 TLB Invalid exceptions
> 
> This version removes pte_sw_mkyoung without polluting MM code and makes
> page fault delay of MIPS on par with other architecture and covers both
> no-RIXI and RIXI MIPS CPUS
> 
> [1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
> -maobibo@xxxxxxxxxxx/
> ---
> V3:
> - reformat with whitespace cleaned up following Thomas's advice
> V2:
> - remove unused asm-generic definition of pte_sw_mkyoung following Mao's
> advice
> ---
> Co-developed-by: Huang Pei <huangpei@xxxxxxxxxxx>
> Signed-off-by: Huang Pei <huangpei@xxxxxxxxxxx>
> Co-developed-by: Bibo Mao <maobibo@xxxxxxxxxx>
> ---
>  arch/mips/include/asm/pgtable.h | 10 ++++------
>  arch/mips/mm/cache.c            | 25 +++++++++++++------------
>  include/linux/pgtable.h         |  8 --------
>  mm/memory.c                     |  3 ---
>  4 files changed, 17 insertions(+), 29 deletions(-)
> 
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index dd7a0f552cac..931fb35730f0 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -27,11 +27,11 @@ struct vm_area_struct;
>  
>  #define PAGE_NONE	__pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
>  				 _page_cachable_default)
> -#define PAGE_SHARED	__pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> -				 _page_cachable_default)
> +#define PAGE_SHARED    __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> +				 __READABLE | _page_cachable_default)
>  #define PAGE_COPY	__pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> -				 _page_cachable_default)
> -#define PAGE_READONLY	__pgprot(_PAGE_PRESENT | \
> +				 __READABLE | _page_cachable_default)
> +#define PAGE_READONLY	__pgprot(_PAGE_PRESENT |  __READABLE | \
>  				 _page_cachable_default)
>  #define PAGE_KERNEL	__pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
>  				 _PAGE_GLOBAL | _page_cachable_default)
> @@ -414,8 +414,6 @@ static inline pte_t pte_mkyoung(pte_t pte)
>  	return pte;
>  }
>  
> -#define pte_sw_mkyoung	pte_mkyoung
> -
>  #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
>  static inline int pte_huge(pte_t pte)	{ return pte_val(pte) & _PAGE_HUGE; }
>  
> diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> index 3e81ba000096..ed75f2871aad 100644
> --- a/arch/mips/mm/cache.c
> +++ b/arch/mips/mm/cache.c
> @@ -159,22 +159,23 @@ static inline void setup_protection_map(void)
>  {
>  	if (cpu_has_rixi) {
>  		protection_map[0]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> +		protection_map[1]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
>  		protection_map[2]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> -		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> +		protection_map[3]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +		protection_map[4]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[5]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[6]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[7]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
>  
>  		protection_map[8]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> -		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> +		protection_map[9]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
>  		protection_map[10] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | _PAGE_NO_READ);
> -		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
> -		protection_map[12] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[13] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> -		protection_map[14] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> -		protection_map[15] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> +		protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | __READABLE);
> +		protection_map[12]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[13]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> +		protection_map[14]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +		protection_map[15]  = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> +
>  
>  	} else {
>  		protection_map[0] = PAGE_NONE;
> diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
> index e8cbc2e795d5..ef9c5fa8673e 100644
> --- a/include/linux/pgtable.h
> +++ b/include/linux/pgtable.h
> @@ -377,14 +377,6 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
>   * To be differentiate with macro pte_mkyoung, this macro is used on platforms
>   * where software maintains page access bit.
>   */
> -#ifndef pte_sw_mkyoung
> -static inline pte_t pte_sw_mkyoung(pte_t pte)
> -{
> -	return pte;
> -}
> -#define pte_sw_mkyoung	pte_sw_mkyoung
> -#endif
> -
>  #ifndef pte_savedwrite
>  #define pte_savedwrite pte_write
>  #endif
> diff --git a/mm/memory.c b/mm/memory.c
> index 602f4283122f..5100ab5bcf77 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -2705,7 +2705,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
>  		}
>  		flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
>  		entry = mk_pte(new_page, vma->vm_page_prot);
> -		entry = pte_sw_mkyoung(entry);
>  		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  		/*
>  		 * Clear the pte entry and flush it first, before updating the
> @@ -3386,7 +3385,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
>  	__SetPageUptodate(page);
>  
>  	entry = mk_pte(page, vma->vm_page_prot);
> -	entry = pte_sw_mkyoung(entry);
>  	if (vma->vm_flags & VM_WRITE)
>  		entry = pte_mkwrite(pte_mkdirty(entry));
>  
> @@ -3661,7 +3659,6 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page)
>  
>  	flush_icache_page(vma, page);
>  	entry = mk_pte(page, vma->vm_page_prot);
> -	entry = pte_sw_mkyoung(entry);
>  	if (write)
>  		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
>  	/* copy-on-write page */
> -- 
> 2.17.1
> 





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