From: Nicușor Cîțu <nc...@bitdefender.com>

This event is sent when the current instruction has been single stepped
as a result of a KVMI_EVENT_PF event to which the introspection tool
set the singlestep field and responded with CONTINUE.

Signed-off-by: Nicușor Cîțu <nc...@bitdefender.com>
Signed-off-by: Adalbert Lazăr <ala...@bitdefender.com>
---
 Documentation/virtual/kvm/kvmi.rst | 25 +++++++++++++++++++
 virt/kvm/kvmi.c                    | 40 ++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+)

diff --git a/Documentation/virtual/kvm/kvmi.rst 
b/Documentation/virtual/kvm/kvmi.rst
index 8721a470de87..572abab1f6ef 100644
--- a/Documentation/virtual/kvm/kvmi.rst
+++ b/Documentation/virtual/kvm/kvmi.rst
@@ -1574,3 +1574,28 @@ introspection has been enabled for this event (see 
**KVMI_CONTROL_EVENTS**).
        KVMI_DESC_TR
 
 ``write`` is 1 if the descriptor was written, 0 otherwise.
+
+12. KVMI_EVENT_SINGLESTEP
+-------------------------
+
+:Architectures: x86
+:Versions: >= 1
+:Actions: CONTINUE, CRASH
+:Parameters:
+
+::
+
+       struct kvmi_event;
+
+:Returns:
+
+::
+
+       struct kvmi_vcpu_hdr;
+       struct kvmi_event_reply;
+
+This event is sent when the current instruction has been executed
+(as a result of a *KVMI_EVENT_PF* event to which the introspection
+tool set the ``singlestep`` field and responded with *CONTINUE*)
+and the introspection has been enabled for this event
+(see **KVMI_CONTROL_EVENTS**).
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index a3a5af9080a9..3dfedf3ae739 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -1182,6 +1182,44 @@ void kvmi_trap_event(struct kvm_vcpu *vcpu)
        kvmi_put(vcpu->kvm);
 }
 
+static u32 kvmi_send_singlestep(struct kvm_vcpu *vcpu)
+{
+       int err, action;
+
+       err = kvmi_send_event(vcpu, KVMI_EVENT_SINGLESTEP, NULL, 0,
+                             NULL, 0, &action);
+       if (err)
+               return KVMI_EVENT_ACTION_CONTINUE;
+
+       return action;
+}
+
+static void __kvmi_singlestep_event(struct kvm_vcpu *vcpu)
+{
+       u32 action;
+
+       action = kvmi_send_singlestep(vcpu);
+       switch (action) {
+       case KVMI_EVENT_ACTION_CONTINUE:
+               break;
+       default:
+               kvmi_handle_common_event_actions(vcpu, action, "SINGLESTEP");
+       }
+}
+
+static void kvmi_singlestep_event(struct kvm_vcpu *vcpu)
+{
+       struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+
+       if (!ivcpu->ss_requested)
+               return;
+
+       if (is_event_enabled(vcpu, KVMI_EVENT_SINGLESTEP))
+               __kvmi_singlestep_event(vcpu);
+
+       ivcpu->ss_requested = false;
+}
+
 static bool __kvmi_create_vcpu_event(struct kvm_vcpu *vcpu)
 {
        u32 action;
@@ -1616,6 +1654,8 @@ void kvmi_stop_ss(struct kvm_vcpu *vcpu)
 
        ivcpu->ss_owner = false;
 
+       kvmi_singlestep_event(vcpu);
+
 out:
        kvmi_put(kvm);
 }
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