[RFC PATCH v6 17/92] kvm: introspection: introduce event actions

[Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>]

From: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>

All vCPU event replies contains the action requested by the introspection
tool, which can be one of the following:

  * KVMI_EVENT_ACTION_CONTINUE
  * KVMI_EVENT_ACTION_RETRY
  * KVMI_EVENT_ACTION_CRASH

The CONTINUE action can be seen as "continue with the old KVM code
path", while the RETRY action as "re-enter guest".

Note: KVMI_EVENT_UNHOOK, a VM event, doesn't have/need a reply.

Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Mihai Donțu <mdontu@xxxxxxxxxxxxxxx>
Co-developed-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
 Documentation/virtual/kvm/kvmi.rst | 10 ++++++++
 include/uapi/linux/kvmi.h          |  4 +++
 kernel/signal.c                    |  1 +
 virt/kvm/kvmi.c                    | 40 ++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+)

diff --git a/Documentation/virtual/kvm/kvmi.rst b/Documentation/virtual/kvm/kvmi.rst
index e7d9a3816e00..1ea4be0d5a45 100644
--- a/Documentation/virtual/kvm/kvmi.rst
+++ b/Documentation/virtual/kvm/kvmi.rst
@@ -482,4 +482,14 @@ with two common structures::
 		__u32 padding2;
 	};
 
+All events accept the KVMI_EVENT_ACTION_CRASH action, which stops the
+guest ungracefully but as soon as possible.
+
+Most of the events accept the KVMI_EVENT_ACTION_CONTINUE action, which
+lets the instruction that caused the event to continue (unless specified
+otherwise).
+
+Some of the events accept the KVMI_EVENT_ACTION_RETRY action, to continue
+by re-entering the guest.
+
 Specific data can follow these common structures.
diff --git a/include/uapi/linux/kvmi.h b/include/uapi/linux/kvmi.h
index dda2ae352611..ccf2239b5db4 100644
--- a/include/uapi/linux/kvmi.h
+++ b/include/uapi/linux/kvmi.h
@@ -66,6 +66,10 @@ enum {
 	KVMI_NUM_EVENTS
 };
 
+#define KVMI_EVENT_ACTION_CONTINUE      0
+#define KVMI_EVENT_ACTION_RETRY         1
+#define KVMI_EVENT_ACTION_CRASH         2
+
 #define KVMI_MSG_SIZE (4096 - sizeof(struct kvmi_msg_hdr))
 
 struct kvmi_msg_hdr {
diff --git a/kernel/signal.c b/kernel/signal.c
index 57b7771e20d7..9befbfaaa710 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1413,6 +1413,7 @@ int kill_pid_info(int sig, struct kernel_siginfo *info, struct pid *pid)
 		 */
 	}
 }
+EXPORT_SYMBOL(kill_pid_info);
 
 static int kill_proc_info(int sig, struct kernel_siginfo *info, pid_t pid)
 {
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index 3cc7bb035796..0d3560b74f2d 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -511,6 +511,46 @@ void kvmi_destroy_vm(struct kvm *kvm)
 	wait_for_completion_killable(&kvm->kvmi_completed);
 }
 
+static int kvmi_vcpu_kill(int sig, struct kvm_vcpu *vcpu)
+{
+	int err = -ESRCH;
+	struct pid *pid;
+	struct kernel_siginfo siginfo[1] = {};
+
+	rcu_read_lock();
+	pid = rcu_dereference(vcpu->pid);
+	if (pid)
+		err = kill_pid_info(sig, siginfo, pid);
+	rcu_read_unlock();
+
+	return err;
+}
+
+static void kvmi_vm_shutdown(struct kvm *kvm)
+{
+	int i;
+	struct kvm_vcpu *vcpu;
+
+	kvm_for_each_vcpu(i, vcpu, kvm)
+		kvmi_vcpu_kill(SIGTERM, vcpu);
+}
+
+void kvmi_handle_common_event_actions(struct kvm_vcpu *vcpu, u32 action,
+				      const char *str)
+{
+	struct kvm *kvm = vcpu->kvm;
+
+	switch (action) {
+	case KVMI_EVENT_ACTION_CRASH:
+		kvmi_vm_shutdown(kvm);
+		break;
+
+	default:
+		kvmi_err(IKVM(kvm), "Unsupported action %d for event %s\n",
+			 action, str);
+	}
+}
+
 void kvmi_run_jobs(struct kvm_vcpu *vcpu)
 {
 	struct kvmi_vcpu *ivcpu = IVCPU(vcpu);