On Sat, Nov 17, 2012 at 06:56:10AM -0800, Linus Torvalds wrote:

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 (plus we would
have no way to ever know we even got the code right, since presumably
we'd never find hardware that actually shows the behavior we'd be
looking for..)

Hmm, touching some wrong page through the stale TLB entry could be a
pretty nasty issue to debug. But you're probably right: how does one
test cheaply whether a PTE just got kicked out of the TLB? Maybe mark it
not-present but this would force a rewalk in the case when it is shared,
which is penalty we don't want to pay.

Oh well...

-- 
Regards/Gruss,
Boris.

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