perf/core: Use static_call to optimize perf_guest_info_callbacks

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Use static_call to optimize perf's guest callbacks on arm64 and x86,
which are now the only architectures that define the callbacks.  Use
DEFINE_STATIC_CALL_RET0 as the default/NULL for all guest callbacks, as
the callback semantics are that a return value '0' means "not in guest".

static_call obviously avoids the overhead of CONFIG_RETPOLINE=y, but is
also advantageous versus other solutions, e.g. per-cpu callbacks, in that
a per-cpu memory load is not needed to detect the !guest case.

Based on code from Peter and Like.

Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lore.kernel.org/r/20211111020738.2512932-10-seanjc@google.com

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Sean Christopherson 2021-11-11 02:07:30 +00:00 • committed by Peter Zijlstra

parent 2aef6f306b

commit 87b940a067

2 changed files with 23 additions and 26 deletions

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34

include/linux/perf_event.h

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15

kernel/events/core.c

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