NIIBE Yutaka wrote:
To have same semantics as other archs, I think that VIPT-WB cache
machine should have cache flush at ptep_set_wrprotect, so that memory
of the page has up-to-date data. Yes, it will be huge performance
impact for fork. But I don't find any good solution other than this
yet.
I think we could do something like (only for VIPT-WB cache machine):
- static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned
long address, pte_t *ptep)
+ static inline void ptep_set_wrprotect(struct vm_area_struct *vma,
struct mm_struct *mm, unsigned long addr, pte_t *ptep)
{
pte_t old_pte = *ptep;
+ if (atomic_read(&mm->mm_users) > 1)
+ flush_cache_page(vma, addr, pte_pfn(old_pte));
set_pte_at(mm, addr, ptep, pte_wrprotect(old_pte));
}
Here, we can add condition for the call of flush_cache_page
to avoid big performance impact for non threads case.
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