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Date: Tue, 21 Sep 2021 17:05:26 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...hat.com>,
Arnaldo Carvalho de Melo <acme@...nel.org>,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Marc Zyngier <maz@...nel.org>, Guo Ren <guoren@...nel.org>,
Nick Hu <nickhu@...estech.com>,
Greentime Hu <green.hu@...il.com>,
Vincent Chen <deanbo422@...il.com>,
Paul Walmsley <paul.walmsley@...ive.com>,
Palmer Dabbelt <palmer@...belt.com>,
Albert Ou <aou@...s.berkeley.edu>,
Paolo Bonzini <pbonzini@...hat.com>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Juergen Gross <jgross@...e.com>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
Jiri Olsa <jolsa@...hat.com>,
Namhyung Kim <namhyung@...nel.org>,
James Morse <james.morse@....com>,
Alexandru Elisei <alexandru.elisei@....com>,
Suzuki K Poulose <suzuki.poulose@....com>,
Sean Christopherson <seanjc@...gle.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>,
Wanpeng Li <wanpengli@...cent.com>,
Jim Mattson <jmattson@...gle.com>,
Joerg Roedel <joro@...tes.org>,
Stefano Stabellini <sstabellini@...nel.org>,
linux-arm-kernel@...ts.infradead.org,
linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
kvmarm@...ts.cs.columbia.edu, linux-csky@...r.kernel.org,
linux-riscv@...ts.infradead.org, kvm@...r.kernel.org,
xen-devel@...ts.xenproject.org,
Artem Kashkanov <artem.kashkanov@...el.com>,
Like Xu <like.xu.linux@...il.com>,
Zhu Lingshan <lingshan.zhu@...el.com>
Subject: [PATCH v3 09/16] perf/core: Use static_call to optimize perf_guest_info_callbacks
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@...radead.org>
Cc: Like Xu <like.xu.linux@...il.com>
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
include/linux/perf_event.h | 28 ++++++----------------------
kernel/events/core.c | 15 +++++++++++++++
2 files changed, 21 insertions(+), 22 deletions(-)
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index eefa197d5354..d582dfeb4e20 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1240,37 +1240,21 @@ extern void perf_event_bpf_event(struct bpf_prog *prog,
#ifdef CONFIG_GUEST_PERF_EVENTS
extern struct perf_guest_info_callbacks *perf_guest_cbs;
-static inline struct perf_guest_info_callbacks *perf_get_guest_cbs(void)
-{
- /* Reg/unreg perf_guest_cbs waits for readers via synchronize_rcu(). */
- lockdep_assert_preemption_disabled();
+DECLARE_STATIC_CALL(__perf_guest_state, *perf_guest_cbs->state);
+DECLARE_STATIC_CALL(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
+DECLARE_STATIC_CALL(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);
- /* Prevent reloading between a !NULL check and dereferences. */
- return READ_ONCE(perf_guest_cbs);
-}
static inline unsigned int perf_guest_state(void)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- return guest_cbs ? guest_cbs->state() : 0;
+ return static_call(__perf_guest_state)();
}
static inline unsigned long perf_guest_get_ip(void)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- /*
- * Arbitrarily return '0' in the unlikely scenario that the callbacks
- * are unregistered between checking guest state and getting the IP.
- */
- return guest_cbs ? guest_cbs->get_ip() : 0;
+ return static_call(__perf_guest_get_ip)();
}
static inline unsigned int perf_guest_handle_intel_pt_intr(void)
{
- struct perf_guest_info_callbacks *guest_cbs = perf_get_guest_cbs();
-
- if (guest_cbs && guest_cbs->handle_intel_pt_intr)
- return guest_cbs->handle_intel_pt_intr();
- return 0;
+ return static_call(__perf_guest_handle_intel_pt_intr)();
}
extern void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
extern void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index c6ec05809f54..79c8ee1778a4 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6485,12 +6485,23 @@ static void perf_pending_event(struct irq_work *entry)
#ifdef CONFIG_GUEST_PERF_EVENTS
struct perf_guest_info_callbacks *perf_guest_cbs;
+DEFINE_STATIC_CALL_RET0(__perf_guest_state, *perf_guest_cbs->state);
+DEFINE_STATIC_CALL_RET0(__perf_guest_get_ip, *perf_guest_cbs->get_ip);
+DEFINE_STATIC_CALL_RET0(__perf_guest_handle_intel_pt_intr, *perf_guest_cbs->handle_intel_pt_intr);
+
void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
{
if (WARN_ON_ONCE(perf_guest_cbs))
return;
WRITE_ONCE(perf_guest_cbs, cbs);
+ static_call_update(__perf_guest_state, cbs->state);
+ static_call_update(__perf_guest_get_ip, cbs->get_ip);
+
+ /* Implementing ->handle_intel_pt_intr is optional. */
+ if (cbs->handle_intel_pt_intr)
+ static_call_update(__perf_guest_handle_intel_pt_intr,
+ cbs->handle_intel_pt_intr);
}
EXPORT_SYMBOL_GPL(perf_register_guest_info_callbacks);
@@ -6500,6 +6511,10 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
return;
WRITE_ONCE(perf_guest_cbs, NULL);
+ static_call_update(__perf_guest_state, (void *)&__static_call_return0);
+ static_call_update(__perf_guest_get_ip, (void *)&__static_call_return0);
+ static_call_update(__perf_guest_handle_intel_pt_intr,
+ (void *)&__static_call_return0);
synchronize_rcu();
}
EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
--
2.33.0.464.g1972c5931b-goog
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