From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Marc Zyngier <maz@kernel.org>, Guo Ren <guoren@kernel.org>,
Nick Hu <nickhu@andestech.com>, Greentime Hu <green.hu@gmail.com>,
Vincent Chen <deanbo422@gmail.com>,
Paul Walmsley <paul.walmsley@sifive.com>,
Palmer Dabbelt <palmer@dabbelt.com>,
Albert Ou <aou@eecs.berkeley.edu>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
Juergen Gross <jgross@suse.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
James Morse <james.morse@arm.com>,
Alexandru Elisei <alexandru.elisei@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Stefano Stabellini <sstabellini@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, linux-csky@vger.kernel.org,
linux-riscv@lists.infradead.org, kvm@vger.kernel.org,
xen-devel@lists.xenproject.org,
Artem Kashkanov <artem.kashkanov@intel.com>,
Like Xu <like.xu.linux@gmail.com>,
Zhu Lingshan <lingshan.zhu@intel.com>
Subject: Re: [PATCH v3 09/16] perf/core: Use static_call to optimize perf_guest_info_callbacks
Date: Wed, 22 Sep 2021 08:33:14 +0200 [thread overview]
Message-ID: <5ad3e3f9-260b-52b2-e0c8-9ab824e08fb4@redhat.com> (raw)
In-Reply-To: <20210922000533.713300-10-seanjc@google.com>
On 22/09/21 02:05, Sean Christopherson wrote:
> 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>
> Cc: Like Xu <like.xu.linux@gmail.com>
> Signed-off-by: Sean Christopherson <seanjc@google.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);
>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
next prev parent reply other threads:[~2021-09-22 6:33 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-22 0:05 [PATCH v3 00/16] perf: KVM: Fix, optimize, and clean up callbacks Sean Christopherson
2021-09-22 0:05 ` [PATCH v3 01/16] perf: Ensure perf_guest_cbs aren't reloaded between !NULL check and deref Sean Christopherson
2021-11-04 9:32 ` Like Xu
2021-11-04 14:18 ` Sean Christopherson
2021-11-10 11:07 ` Paolo Bonzini
2021-11-11 0:39 ` Sean Christopherson
2021-09-22 0:05 ` [PATCH v3 02/16] KVM: x86: Register perf callbacks after calling vendor's hardware_setup() Sean Christopherson
2021-09-22 6:23 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 03/16] KVM: x86: Register Processor Trace interrupt hook iff PT enabled in guest Sean Christopherson
2021-09-22 6:24 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 04/16] perf: Stop pretending that perf can handle multiple guest callbacks Sean Christopherson
2021-09-22 6:25 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 05/16] perf: Drop dead and useless guest "support" from arm, csky, nds32 and riscv Sean Christopherson
2021-09-22 6:26 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 06/16] perf/core: Rework guest callbacks to prepare for static_call support Sean Christopherson
2021-09-22 6:28 ` Paolo Bonzini
2021-09-22 18:31 ` Boris Ostrovsky
2021-09-22 0:05 ` [PATCH v3 07/16] perf: Add wrappers for invoking guest callbacks Sean Christopherson
2021-09-22 6:29 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 08/16] perf: Force architectures to opt-in to " Sean Christopherson
2021-09-22 6:32 ` Paolo Bonzini
2021-09-22 14:48 ` Sean Christopherson
2021-11-09 23:46 ` Sean Christopherson
2021-09-22 0:05 ` [PATCH v3 09/16] perf/core: Use static_call to optimize perf_guest_info_callbacks Sean Christopherson
2021-09-22 6:33 ` Paolo Bonzini [this message]
2021-09-22 0:05 ` [PATCH v3 10/16] KVM: x86: Drop current_vcpu for kvm_running_vcpu + kvm_arch_vcpu variable Sean Christopherson
2021-09-22 6:40 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 11/16] KVM: x86: More precisely identify NMI from guest when handling PMI Sean Christopherson
2021-09-22 6:38 ` Paolo Bonzini
2021-09-22 0:05 ` [PATCH v3 12/16] KVM: Move x86's perf guest info callbacks to generic KVM Sean Christopherson
2021-09-22 6:41 ` Paolo Bonzini
2021-10-11 9:35 ` Marc Zyngier
2021-10-11 14:46 ` Sean Christopherson
2021-10-11 15:33 ` Marc Zyngier
2021-09-22 0:05 ` [PATCH v3 13/16] KVM: x86: Move Intel Processor Trace interrupt handler to vmx.c Sean Christopherson
2021-09-22 0:05 ` [PATCH v3 14/16] KVM: arm64: Convert to the generic perf callbacks Sean Christopherson
2021-10-11 9:38 ` Marc Zyngier
2021-09-22 0:05 ` [PATCH v3 15/16] KVM: arm64: Drop perf.c and fold its tiny bits of code into arm.c / pmu.c Sean Christopherson
2021-10-11 9:44 ` Marc Zyngier
2021-11-09 23:16 ` Sean Christopherson
2021-09-22 0:05 ` [PATCH v3 16/16] perf: Drop guest callback (un)register stubs Sean Christopherson
2021-09-22 6:29 ` Paolo Bonzini
2021-09-22 6:42 ` [PATCH v3 00/16] perf: KVM: Fix, optimize, and clean up callbacks Paolo Bonzini
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