Messages in this thread | | | Subject | Re: [PATCH 10/26] x86, pkeys: notify userspace about protection key faults | From | Dave Hansen <> | Date | Sun, 27 Sep 2015 15:39:58 -0700 |
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On 09/25/2015 11:20 PM, Ingo Molnar wrote: > * Dave Hansen <dave@sr71.net> wrote: ... >> Since follow_pte() fails for all huge >> pages, it just falls back to pulling the protection key out of the VMA, >> which _does_ work for huge pages. > > That might be true for explicit hugetlb vmas, but what about transparent hugepages > that can show up in regular vmas?
All PTEs (large or small) established under a given VMA have the same protection key. Any change in protection key for a range will either change or split the VMA.
So I think it's safe to rely on the VMA entirely. Well, as least as safe as the PTE. It's definitely a wee bit racy, which I'll elaborate on when I repost the patches.
>> I've actually removed the PTE walking and I just now use the VMA directly. I >> don't see a ton of additional value from walking the page tables when we can get >> what we need from the VMA. > > That's actually good, because it's also cheap, especially if we can get rid of the > extra find_vma(). > > and we (thankfully) have no non-linear vmas to worry about anymore.
Yep.
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