[PATCH v3 08/16] perf: Force architectures to opt-in to guest callbacks

Sean Christopherson
2021-09-22T00:06:29Z

Introduce GUEST_PERF_EVENTS and require architectures to select it to
allow registering and using guest callbacks in perf. This will hopefully
make it more difficult for new architectures to add useless "support" for
guest callbacks, e.g. via copy+paste.

Stubbing out the helpers has the happy bonus of avoiding a load of
perf_guest_cbs when GUEST_PERF_EVENTS=n on arm64/x86.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/arm64/kvm/Kconfig | 1 +
arch/x86/kvm/Kconfig | 1 +
arch/x86/xen/Kconfig | 1 +
include/linux/perf_event.h | 6 ++++++
init/Kconfig | 4 ++++
kernel/events/core.c | 2 ++
6 files changed, 15 insertions(+)

diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index a4eba0908bfa..f2121404c7c6 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -37,6 +37,7 @@ menuconfig KVM
select HAVE_KVM_IRQ_BYPASS
select HAVE_KVM_VCPU_RUN_PID_CHANGE
select SCHED_INFO
+ select GUEST_PERF_EVENTS if PERF_EVENTS
help
Support hosting virtualized guest machines.

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index ac69894eab88..699bf786fbce 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -36,6 +36,7 @@ config KVM
select KVM_MMIO
select SCHED_INFO
select PERF_EVENTS
+ select GUEST_PERF_EVENTS
select HAVE_KVM_MSI
select HAVE_KVM_CPU_RELAX_INTERCEPT
select HAVE_KVM_NO_POLL
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index afc1da68b06d..d07595a9552d 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -23,6 +23,7 @@ config XEN_PV
select PARAVIRT_XXL
select XEN_HAVE_PVMMU
select XEN_HAVE_VPMU
+ select GUEST_PERF_EVENTS
help
Support running as a Xen PV guest.

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index c0a6eaf55fb1..eefa197d5354 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -1238,6 +1238,7 @@ extern void perf_event_bpf_event(struct bpf_prog *prog,
enum perf_bpf_event_type type,
u16 flags);

+#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)
{
@@ -1273,6 +1274,11 @@ static inline unsigned int perf_guest_handle_intel_pt_intr(void)
}
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);
+#else
+static inline unsigned int perf_guest_state(void) { return 0; }
+static inline unsigned long perf_guest_get_ip(void) { return 0; }
+static inline unsigned int perf_guest_handle_intel_pt_intr(void) { return 0; }
+#endif /* CONFIG_GUEST_PERF_EVENTS */

extern void perf_event_exec(void);
extern void perf_event_comm(struct task_struct *tsk, bool exec);
diff --git a/init/Kconfig b/init/Kconfig
index 55f9f7738ebb..acc7e8ba4563 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -1776,6 +1776,10 @@ config HAVE_PERF_EVENTS
help
See tools/perf/design.txt for details.

+config GUEST_PERF_EVENTS
+ bool
+ depends on HAVE_PERF_EVENTS
+
config PERF_USE_VMALLOC
bool
help
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2e3dc9fbd5d9..c6ec05809f54 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6482,6 +6482,7 @@ static void perf_pending_event(struct irq_work *entry)
perf_swevent_put_recursion_context(rctx);
}

+#ifdef CONFIG_GUEST_PERF_EVENTS
struct perf_guest_info_callbacks *perf_guest_cbs;

void perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
@@ -6502,6 +6503,7 @@ void perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *cbs)
synchronize_rcu();
}
EXPORT_SYMBOL_GPL(perf_unregister_guest_info_callbacks);
+#endif

static void
perf_output_sample_regs(struct perf_output_handle *handle,
--
2.33.0.464.g1972c5931b-goog