Messages in this thread | | | Subject | Re: [PATCH v17 11/26] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW | From | "Yu, Yu-cheng" <> | Date | Tue, 26 Jan 2021 08:45:06 -0800 |
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On 1/26/2021 2:24 AM, Borislav Petkov wrote: > On Mon, Jan 25, 2021 at 02:18:37PM -0800, Yu, Yu-cheng wrote: >> For example, when a thread reads a W=1, D=0 PTE and before changing it to >> W=0,D=0, another thread could have written to the page and the PTE is W=1, >> D=1 now. When try_cmpxchg() detects the difference, old_pte is read again. > > None of that is mentioned in the comment above it and if anything, > *that* is what should be explained there - not some guarantee about some > processors which doesn't even apply here. > > Also, add the fact that try_cmpxchg() will update old_pte with any > modified bits - D=1 for example - when it fails. As Peter just explained > to me on IRC. > > Thx. >
Yes, I will fix it. Thanks!
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