Messages in this thread | | | Date | Sat, 17 Nov 2012 10:24:35 -0500 | From | Rik van Riel <> | Subject | Re: [PATCH 2/3] x86,mm: drop TLB flush from ptep_set_access_flags |
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On 11/17/2012 09:56 AM, Linus Torvalds wrote: > On Sat, Nov 17, 2012 at 6:50 AM, Borislav Petkov <bp@alien8.de> wrote: >> I don't know, however, whether it would be prudent to have some sort of >> a cheap assertion in the code (cheaper than INVLPG %ADDR, although on >> older cpus we do MOV CR3) just in case. This should be enabled only with >> DEBUG_VM on, of course... > > I wonder how we could actually test for it. We'd have to have some > per-cpu page-fault address check (along with a generation count on the > mm or similar). I doubt we'd figure out anything that works reliably > and efficiently and would actually show any problems
Would it be enough to simply print out a warning if we fault on the same address twice (or three times) in a row, and then flush the local TLB?
I realize this would not just trigger on CPUs that fail to invalidate TLB entries that cause faults, but also on kernel paths that cause a page fault to be re-taken...
... but then again, don't we want to find those paths and fix them, anyway? :)
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