KVM: x86: Add RIP to the kvm_entry, i.e. VM-Enter, tracepoint

Add RIP to the kvm_entry tracepoint to help debug if the kvm_exit
tracepoint is disabled or if VM-Enter fails, in which case the kvm_exit
tracepoint won't be hit.

Read RIP from within the tracepoint itself to avoid a potential VMREAD
and retpoline if the guest's RIP isn't available.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <20200923201349.16097-2-sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/trace.h

@@ -15,18 +15,20 @@
  * Tracepoint for guest mode entry.
  */
 TRACE_EVENT(kvm_entry,
-	TP_PROTO(unsigned int vcpu_id),
-	TP_ARGS(vcpu_id),
+	TP_PROTO(struct kvm_vcpu *vcpu),
+	TP_ARGS(vcpu),
 
 	TP_STRUCT__entry(
 		__field(	unsigned int,	vcpu_id		)
+		__field(	unsigned long,	rip		)
 	),
 
 	TP_fast_assign(
-		__entry->vcpu_id	= vcpu_id;
+		__entry->vcpu_id        = vcpu->vcpu_id;
+		__entry->rip		= kvm_rip_read(vcpu);
 	),
 
-	TP_printk("vcpu %u", __entry->vcpu_id)
+	TP_printk("vcpu %u, rip 0x%lx", __entry->vcpu_id, __entry->rip)
 );
 
 /*

arch/x86/kvm/x86.c

@@ -8563,7 +8563,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 		kvm_x86_ops.request_immediate_exit(vcpu);
 	}
 
-	trace_kvm_entry(vcpu->vcpu_id);
+	trace_kvm_entry(vcpu);
 
 	fpregs_assert_state_consistent();
 	if (test_thread_flag(TIF_NEED_FPU_LOAD))