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SubjectRe: 2.6.{26.2,27-rc} oops on virtualbox
One thing that I think really needs to be considered is that the current 
PV stubs are (a) large, and (b) non-atomic.

In the case at hand we have:

c012fc69: 51 push %ecx
c012fc6a: 52 push %edx
c012fc6b: ff 15 40 b9 41 c0 call *0xc041b940
c012fc71: 5a pop %edx
c012fc72: 59 pop %ecx

Ten bytes replacing a two-byte native sequence.

If this was done as a call to an out-of-line stub, it would be only five
bytes, which would reduce native icache overhead from 400% to 150%, but
perhaps more importantly, it would not be subject to returns inside the
sequence itself (since the out-of-line stub would still exist.) As an
optional bonus, at least on 32 bits the indirect call could be replaced
with a direct call in the out-of-line stub.

-hpa


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