[Xen-devel] [PATCH 0/4] x86: reduce Meltdown band-aid overhead a little further

["Jan Beulich" <JBeulich@xxxxxxxx>]

Prereq: x86: slightly reduce Meltdown band-aid overhead
(https://lists.xenproject.org/archives/html/xen-devel/2018-01/msg01609.html)

The overall effect of this series is smaller than that of the single
patch above (up to 1% in my measurements, but again instead
of the almost 40% loss of performance George has seen that
system showed a 10-13% decline "only"), but perhaps still worth
considering.

1: remove CR reads from exit-to-guest path
2: eliminate most XPTI entry/exit code when it's not in use
3: re-organize toggle_guest_*()
4: avoid double CR3 reload when switching to guest user mode

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>


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