Messages in this thread | | | Date | Fri, 31 Aug 2018 11:53:00 +0200 | From | Peter Zijlstra <> | Subject | Re: [RFC PATCH v3 12/24] x86/mm: Modify ptep_set_wrprotect and pmdp_set_wrprotect for _PAGE_DIRTY_SW |
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On Thu, Aug 30, 2018 at 11:47:16PM +0200, Jann Horn wrote: > do { > pte = pte_wrprotect(pte); > /* note: relies on _PAGE_DIRTY_HW < _PAGE_DIRTY_SW */ > /* dirty direct bit-twiddling; you can probably write > this in a nicer way */ > pte.pte |= (pte.pte & _PAGE_DIRTY_HW) >> > _PAGE_BIT_DIRTY_HW << _PAGE_BIT_DIRTY_SW; > pte.pte &= ~_PAGE_DIRTY_HW; > pte = cmpxchg(ptep, pte, new_pte); > } while (pte != new_pte);
Please use the form:
pte_t new_pte, pte = READ_ONCE(*ptep); do { new_pte = /* ... */; } while (!try_cmpxchg(ptep, &pte, new_pte);
Also, this will fail to build on i386-PAE, but I suspect this code will be under some CONFIG option specific to x86_64 anyway.
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