Messages in this thread | | | Date | Fri, 22 Jul 2016 22:11:05 +0200 | From | Ingo Molnar <> | Subject | Re: [kernel-hardening] [PATCH v5 03/32] x86/cpa: In populate_pgd, don't set the pgd entry until it's populated |
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* Andy Lutomirski <luto@amacapital.net> wrote:
> This garbage (as evidenced by my bug and my failed attempt to fix it) > only works if you never have a low-level page table that isn't linked > into a higher-level page table, and it mostly requires you to do > everything exactly the way it was originally done so all the horrible > inline helpers don't get confused. > > And AFAICT all of this was done to manually unroll a loop, and I bet > it never sped anything up measurably even on 386 or PPro. > > Whenever some vendor releases a 5 level page table CPU, can we > *please* clean this up first? We should have a type that points to a > table, a different type that points to an entry (or maybe not have > pointers to entries at all), and the levels should be referred to by > *number*. When you need to traverse all the way down, you write a > *loop* instead of four bloody helper functions, some of which are > incomprehensibly no-ops on some kernels. And if this means that, on > Intel, we have a silly branch in the inner loop because the bottom > level entry format is special, who cares? > </rant>
I'd welcome (and help out!) any effort to clean it up gradually.
Thanks,
Ingo
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