In certain situations (when the guest has to be paused, suspended,
migrated, etc.), userspace/QEMU will use the KVM_INTROSPECTION_UNHOOK
ioctl in order to trigger the KVMI_EVENT_UNHOOK. If the event is sent
successfully (the VM has an active introspection channel), userspace
should delay the action (pause/suspend/...) to give the introspection
tool the chance to remove its hooks (eg. breakpoints). Once a timeout
is reached or the introspection tool has closed the socket, QEMU should
continue with the planned action.
Signed-off-by: Adalbert Lazăr <alazar@xxxxxxxxxxxxxxx>
---
Documentation/virtual/kvm/kvmi.rst | 20 ++++++++++++++++++
virt/kvm/kvmi.c | 34 +++++++++++++++++++++++++++++-
virt/kvm/kvmi_int.h | 1 +
virt/kvm/kvmi_msg.c | 20 ++++++++++++++++++
4 files changed, 74 insertions(+), 1 deletion(-)
diff --git a/Documentation/virtual/kvm/kvmi.rst b/Documentation/virtual/kvm/kvmi.rst
index 1ea4be0d5a45..28e1a1c80551 100644
--- a/Documentation/virtual/kvm/kvmi.rst
+++ b/Documentation/virtual/kvm/kvmi.rst
@@ -493,3 +493,23 @@ 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.
+
+1. KVMI_EVENT_UNHOOK
+--------------------
+
+:Architecture: all
+:Versions: >= 1
+:Actions: CONTINUE, CRASH
+:Parameters:
+
+::
+
+ struct kvmi_event;
+
+:Returns: none
+
+This event is sent when the device manager (ie. QEMU) has to
+pause/stop/migrate the guest (see **Unhooking**) and the introspection
+has been enabled for this event (see **KVMI_CONTROL_VM_EVENTS**).
+The introspection tool has a chance to unhook and close the KVMI channel
+(signaling that the operation can proceed).
diff --git a/virt/kvm/kvmi.c b/virt/kvm/kvmi.c
index 0d3560b74f2d..7eda49bf65c4 100644
--- a/virt/kvm/kvmi.c
+++ b/virt/kvm/kvmi.c
@@ -644,6 +644,9 @@ int kvmi_cmd_control_vm_events(struct kvmi *ikvm, unsigned int event_id,
static void kvmi_job_abort(struct kvm_vcpu *vcpu, void *ctx)
{
+ struct kvmi_vcpu *ivcpu = IVCPU(vcpu);
+
+ ivcpu->reply_waiting = false;
}
static void kvmi_abort_events(struct kvm *kvm)
@@ -655,6 +658,34 @@ static void kvmi_abort_events(struct kvm *kvm)
kvmi_add_job(vcpu, kvmi_job_abort, NULL, NULL);
}
+static bool __kvmi_unhook_event(struct kvmi *ikvm)
+{
+ int err;
+
+ if (!test_bit(KVMI_EVENT_UNHOOK, ikvm->vm_ev_mask))
+ return false;
+
+ err = kvmi_msg_send_unhook(ikvm);
+
+ return !err;
+}
+
+static bool kvmi_unhook_event(struct kvm *kvm)
+{
+ struct kvmi *ikvm;
+ bool ret = true;
+
+ ikvm = kvmi_get(kvm);
+ if (!ikvm)
+ return false;
+
+ ret = __kvmi_unhook_event(ikvm);
+
+ kvmi_put(kvm);
+
+ return ret;
+}
+
int kvmi_ioctl_unhook(struct kvm *kvm, bool force_reset)
{
struct kvmi *ikvm;
@@ -664,7 +695,8 @@ int kvmi_ioctl_unhook(struct kvm *kvm, bool force_reset)
if (!ikvm)
return -EFAULT;
- kvm_info("TODO: %s force_reset %d", __func__, force_reset);
+ if (!force_reset && !kvmi_unhook_event(kvm))
+ err = -ENOENT;
kvmi_put(kvm);
diff --git a/virt/kvm/kvmi_int.h b/virt/kvm/kvmi_int.h
index 70c8ca0343a3..9750a9b9902b 100644
--- a/virt/kvm/kvmi_int.h
+++ b/virt/kvm/kvmi_int.h
@@ -123,6 +123,7 @@ bool kvmi_sock_get(struct kvmi *ikvm, int fd);
void kvmi_sock_shutdown(struct kvmi *ikvm);
void kvmi_sock_put(struct kvmi *ikvm);
bool kvmi_msg_process(struct kvmi *ikvm);
+int kvmi_msg_send_unhook(struct kvmi *ikvm);
/* kvmi.c */
void *kvmi_msg_alloc(void);
diff --git a/virt/kvm/kvmi_msg.c b/virt/kvm/kvmi_msg.c
index 536034e1bea7..0c7c1e968007 100644
--- a/virt/kvm/kvmi_msg.c
+++ b/virt/kvm/kvmi_msg.c
@@ -705,3 +705,23 @@ int kvmi_send_event(struct kvm_vcpu *vcpu, u32 ev_id,
return err;
}
+int kvmi_msg_send_unhook(struct kvmi *ikvm)
+{
+ struct kvmi_msg_hdr hdr;
+ struct kvmi_event common;
+ struct kvec vec[] = {
+ {.iov_base = &hdr, .iov_len = sizeof(hdr) },
+ {.iov_base = &common, .iov_len = sizeof(common)},
+ };
+ size_t msg_size = sizeof(hdr) + sizeof(common);
+ size_t n = ARRAY_SIZE(vec);
+
+ memset(&hdr, 0, sizeof(hdr));
+ hdr.id = KVMI_EVENT;
+ hdr.seq = new_seq(ikvm);
+ hdr.size = msg_size - sizeof(hdr);
+
+ kvmi_setup_event_common(&common, KVMI_EVENT_UNHOOK, 0);
+
+ return kvmi_sock_write(ikvm, vec, n, msg_size);
+}
