KVM: x86/pmu: Process only enabled PMCs when emulating events in software

Mask off disabled counters based on PERF_GLOBAL_CTRL *before* iterating
over PMCs to emulate (branch) instruction required events in software.  In
the common case where the guest isn't utilizing the PMU, pre-checking for
enabled counters turns a relatively expensive search into a few AND uops
and a Jcc.

Sadly, PMUs without PERF_GLOBAL_CTRL, e.g. most existing AMD CPUs, are out
of luck as there is no way to check that a PMC isn't being used without
checking the PMC's event selector.

Cc: Konstantin Khorenko <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Sean Christopherson <[email protected]>

0 files changed, 0 insertions, 0 deletions