Re: [PATCH 4/4] MIPS: Sync icache & dcache in set_pte_at

[David Daney <ddaney@caviumnetworks.com>]

On 02/29/2016 06:37 PM, Paul Burton wrote:
[...]
> @@ -234,6 +237,22 @@ static inline void pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *pt
>   }
>   #endif
>
> +static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
> +			      pte_t *ptep, pte_t pteval)
> +{
> +	extern void __update_cache(unsigned long address, pte_t pte);
> +
> +	if (!pte_present(pteval))
> +		goto cache_sync_done;
> +
> +	if (pte_present(*ptep) && (pte_pfn(*ptep) == pte_pfn(pteval)))
> +		goto cache_sync_done;
> +
> +	__update_cache(addr, pteval);
> +cache_sync_done:
> +	set_pte(ptep, pteval);
> +}
> +

This seems crazy.  I don't think any other architecture does this type 
of work in set_pte_at().

Can you look into finding a better way?

What if you ...


>   /*
>    * (pmds are folded into puds so this doesn't get actually called,
>    * but the define is needed for a generic inline function.)
> @@ -430,15 +449,12 @@ static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
>
>   extern void __update_tlb(struct vm_area_struct *vma, unsigned long address,
>   	pte_t pte);
> -extern void __update_cache(struct vm_area_struct *vma, unsigned long address,
> -	pte_t pte);
>
>   static inline void update_mmu_cache(struct vm_area_struct *vma,
>   	unsigned long address, pte_t *ptep)
>   {
>   	pte_t pte = *ptep;
>   	__update_tlb(vma, address, pte);
> -	__update_cache(vma, address, pte);

... Reversed the order of these two operations?

>   }
>
>   static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,
> diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> index 8befa55..bf04c6c 100644
> --- a/arch/mips/mm/cache.c
> +++ b/arch/mips/mm/cache.c
> @@ -125,30 +125,17 @@ void __flush_anon_page(struct page *page, unsigned long vmaddr)
>
>   EXPORT_SYMBOL(__flush_anon_page);
>
> -void __flush_icache_page(struct vm_area_struct *vma, struct page *page)
> -{
> -	unsigned long addr;
> -
> -	if (PageHighMem(page))
> -		return;
> -
> -	addr = (unsigned long) page_address(page);
> -	flush_data_cache_page(addr);
> -}
> -EXPORT_SYMBOL_GPL(__flush_icache_page);
> -
> -void __update_cache(struct vm_area_struct *vma, unsigned long address,
> -	pte_t pte)
> +void __update_cache(unsigned long address, pte_t pte)
>   {
>   	struct page *page;
>   	unsigned long pfn, addr;
> -	int exec = (vma->vm_flags & VM_EXEC) && !cpu_has_ic_fills_f_dc;
> +	int exec = !pte_no_exec(pte) && !cpu_has_ic_fills_f_dc;
>
>   	pfn = pte_pfn(pte);
>   	if (unlikely(!pfn_valid(pfn)))
>   		return;
>   	page = pfn_to_page(pfn);
> -	if (page_mapping(page) && Page_dcache_dirty(page)) {
> +	if (Page_dcache_dirty(page)) {
>   		if (PageHighMem(page))
>   			addr = (unsigned long)kmap_atomic(page);
>   		else
>