Messages in this thread | | | From | Linus Torvalds <> | Date | Mon, 18 Oct 2021 08:15:05 -1000 | Subject | Re: [GIT PULL] KVM fixes for Linux 5.15-rc7 |
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On Mon, Oct 18, 2021 at 8:03 AM Paolo Bonzini <pbonzini@redhat.com> wrote: > > The code is not wrong, there is a comment explaining it: > > * Use a bitwise-OR instead of a logical-OR to aggregate the reserved > * bits and EPT's invalid memtype/XWR checks to avoid an extra Jcc > * (this is extremely unlikely to be short-circuited as true).
That makes very little sense.
It seems to be avoiding a 'jcc' and replace it with a 'setcc' and an 'or'. Which is likely both bigger and slower.
If the jcc were unpredictable, maybe that would be one thing. But at least from a quick look, that doesn't even seem likely
The other use of that function has a "WARN_ONCE()" on it, so presumably it normally doesn't ever trigger either of the boolean conditions.
Very strange code.
Linus
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