KVM: Add a simplified wrapper for registering perf callbacks

Add a parameter-less API for registering perf callbacks in anticipation of
introducing another x86-only parameter for handling mediated PMU PMIs.

No functional change intended.

Acked-by: Anup Patel <anup@brainfault.org>
Tested-by: Xudong Hao <xudong.hao@intel.com>
Tested-by: Manali Shukla <manali.shukla@amd.com>
Link: https://patch.msgid.link/20251206001720.468579-15-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

Author: sean-jc

arch/arm64/kvm/arm.c

@@ -2357,7 +2357,7 @@ static int __init init_subsystems(void)
 	if (err)
 		goto out;
 
-	kvm_register_perf_callbacks(NULL);
+	kvm_register_perf_callbacks();
 
 out:
 	if (err)

arch/loongarch/kvm/main.c

@@ -394,7 +394,7 @@ static int kvm_loongarch_env_init(void)
 	}
 
 	kvm_init_gcsr_flag();
-	kvm_register_perf_callbacks(NULL);
+	kvm_register_perf_callbacks();
 
 	/* Register LoongArch IPI interrupt controller interface. */
 	ret = kvm_loongarch_register_ipi_device();

arch/riscv/kvm/main.c

@@ -174,7 +174,7 @@ static int __init riscv_kvm_init(void)
 
 	kvm_riscv_setup_vendor_features();
 
-	kvm_register_perf_callbacks(NULL);
+	kvm_register_perf_callbacks();
 
 	rc = kvm_init(sizeof(struct kvm_vcpu), 0, THIS_MODULE);
 	if (rc) {

arch/x86/kvm/x86.c

@@ -10107,7 +10107,7 @@ int kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 		set_hv_tscchange_cb(kvm_hyperv_tsc_notifier);
 #endif
 
-	kvm_register_perf_callbacks(ops->handle_intel_pt_intr);
+	__kvm_register_perf_callbacks(ops->handle_intel_pt_intr, NULL);
 
 	if (IS_ENABLED(CONFIG_KVM_SW_PROTECTED_VM) && tdp_mmu_enabled)
 		kvm_caps.supported_vm_types |= BIT(KVM_X86_SW_PROTECTED_VM);

include/linux/kvm_host.h

@@ -1749,10 +1749,17 @@ static inline bool kvm_arch_intc_initialized(struct kvm *kvm)
 #ifdef CONFIG_GUEST_PERF_EVENTS
 unsigned long kvm_arch_vcpu_get_ip(struct kvm_vcpu *vcpu);
 
-void kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void));
+void __kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void),
+				   void (*mediated_pmi_handler)(void));
+
+static inline void kvm_register_perf_callbacks(void)
+{
+	__kvm_register_perf_callbacks(NULL, NULL);
+}
+
 void kvm_unregister_perf_callbacks(void);
 #else
-static inline void kvm_register_perf_callbacks(void *ign) {}
+static inline void kvm_register_perf_callbacks(void) {}
 static inline void kvm_unregister_perf_callbacks(void) {}
 #endif /* CONFIG_GUEST_PERF_EVENTS */
 

virt/kvm/kvm_main.c

@@ -6470,10 +6470,11 @@ static struct perf_guest_info_callbacks kvm_guest_cbs = {
 	.handle_mediated_pmi	= NULL,
 };
 
-void kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void))
+void __kvm_register_perf_callbacks(unsigned int (*pt_intr_handler)(void),
+				   void (*mediated_pmi_handler)(void))
 {
 	kvm_guest_cbs.handle_intel_pt_intr = pt_intr_handler;
-	kvm_guest_cbs.handle_mediated_pmi = NULL;
+	kvm_guest_cbs.handle_mediated_pmi = mediated_pmi_handler;
 
 	perf_register_guest_info_callbacks(&kvm_guest_cbs);
 }