hw/nitro: Introduce Nitro Enclave Heartbeat device
Nitro Enclaves expect the parent instance to host a vsock heartbeat listener at port 9000. To host a Nitro Enclave with the nitro accel in QEMU, add such a heartbeat listener as device model, so that the machine can easily instantiate it. Signed-off-by: Alexander Graf <graf@amazon.com> Link: https://lore.kernel.org/r/20260225220807.33092-7-graf@amazon.com Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Alexander Graf committed
Feb 25, 2026 at 22:08 UTC
9bdc612a18588975f5776ee4e562df607fea1b2c
5 files changed
+148
hw/nitro/Kconfig
+4
@@ -4,3 +4,7 @@ config NITRO_VSOCK_BUS
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config NITRO_SERIAL_VSOCK
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bool
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depends on NITRO_VSOCK_BUS
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+
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+config NITRO_HEARTBEAT
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+ bool
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+ depends on NITRO_VSOCK_BUS
hw/nitro/heartbeat.c
new
+115
@@ -0,0 +1,115 @@
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+/*
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+ * Nitro Enclave Heartbeat device
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+ *
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+ * Copyright © 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
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+ *
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+ * Authors:
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+ * Alexander Graf <graf@amazon.com>
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+ *
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+ * The Nitro Enclave init process sends a heartbeat byte (0xB7) to
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+ * CID 3 (parent) port 9000 on boot to signal it reached initramfs.
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+ * The parent must accept the connection, read the byte, and echo it
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+ * back. If the enclave init cannot reach the listener, it exits.
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+ *
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+ * SPDX-License-Identifier: GPL-2.0-or-later
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+ */
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+
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+#include "qemu/osdep.h"
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+#include "qapi/error.h"
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+#include "chardev/char.h"
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+#include "chardev/char-fe.h"
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+#include "hw/nitro/heartbeat.h"
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+#include "trace.h"
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+
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+#define HEARTBEAT_PORT 9000
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+#define VMADDR_CID_ANY_STR "4294967295"
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+
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+static int nitro_heartbeat_can_read(void *opaque)
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+{
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+ NitroHeartbeatState *s = opaque;
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+
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+ /* One-shot protocol: stop reading after the first heartbeat */
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+ return s->done ? 0 : 1;
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+}
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+
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+static void nitro_heartbeat_read(void *opaque, const uint8_t *buf, int size)
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+{
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+ NitroHeartbeatState *s = opaque;
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+
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+ if (s->done || size < 1) {
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+ return;
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+ }
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+
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+ /* Echo the heartbeat byte back and disconnect */
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+ qemu_chr_fe_write_all(&s->vsock, buf, 1);
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+ s->done = true;
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+ qemu_chr_fe_deinit(&s->vsock, true);
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+
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+ trace_nitro_heartbeat_done();
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+}
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+
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+static void nitro_heartbeat_event(void *opaque, QEMUChrEvent event)
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+{
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+ trace_nitro_heartbeat_event(event);
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+}
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+
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+static void nitro_heartbeat_realize(DeviceState *dev, Error **errp)
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+{
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+ NitroHeartbeatState *s = NITRO_HEARTBEAT(dev);
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+ g_autofree char *chardev_id = NULL;
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+ Chardev *chr;
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+ ChardevBackend *backend;
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+ ChardevSocket *sock;
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+
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+ chardev_id = g_strdup_printf("nitro-heartbeat");
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+
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+ backend = g_new0(ChardevBackend, 1);
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+ backend->type = CHARDEV_BACKEND_KIND_SOCKET;
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+ sock = backend->u.socket.data = g_new0(ChardevSocket, 1);
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+ sock->addr = g_new0(SocketAddressLegacy, 1);
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+ sock->addr->type = SOCKET_ADDRESS_TYPE_VSOCK;
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+ sock->addr->u.vsock.data = g_new0(VsockSocketAddress, 1);
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+ sock->addr->u.vsock.data->cid = g_strdup(VMADDR_CID_ANY_STR);
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+ sock->addr->u.vsock.data->port = g_strdup_printf("%u", HEARTBEAT_PORT);
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+ sock->server = true;
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+ sock->has_server = true;
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+ sock->wait = false;
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+ sock->has_wait = true;
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+
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+ chr = qemu_chardev_new(chardev_id, TYPE_CHARDEV_SOCKET,
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+ backend, NULL, errp);
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+ if (!chr) {
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+ return;
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+ }
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+
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+ if (!qemu_chr_fe_init(&s->vsock, chr, errp)) {
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+ return;
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+ }
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+
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+ qemu_chr_fe_set_handlers(&s->vsock,
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+ nitro_heartbeat_can_read,
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+ nitro_heartbeat_read,
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+ nitro_heartbeat_event,
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+ NULL, s, NULL, true);
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+}
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+
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+static void nitro_heartbeat_class_init(ObjectClass *oc, const void *data)
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+{
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+ DeviceClass *dc = DEVICE_CLASS(oc);
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+
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+ dc->realize = nitro_heartbeat_realize;
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+}
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+
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+static const TypeInfo nitro_heartbeat_info = {
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+ .name = TYPE_NITRO_HEARTBEAT,
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+ .parent = TYPE_NITRO_VSOCK_DEVICE,
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+ .instance_size = sizeof(NitroHeartbeatState),
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+ .class_init = nitro_heartbeat_class_init,
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+};
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+
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+static void nitro_heartbeat_register(void)
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+{
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+ type_register_static(&nitro_heartbeat_info);
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+}
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+
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+type_init(nitro_heartbeat_register);
hw/nitro/meson.build
+1
@@ -1,2 +1,3 @@
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system_ss.add(when: 'CONFIG_NITRO_VSOCK_BUS', if_true: files('nitro-vsock-bus.c'))
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system_ss.add(when: 'CONFIG_NITRO_SERIAL_VSOCK', if_true: files('serial-vsock.c'))
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+system_ss.add(when: 'CONFIG_NITRO_HEARTBEAT', if_true: files('heartbeat.c'))
hw/nitro/trace-events
+4
@@ -2,3 +2,7 @@
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3
# serial-vsock.c
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nitro_serial_vsock_event(int event) "event %d"
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+
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+# heartbeat.c
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+nitro_heartbeat_event(int event) "event %d"
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+nitro_heartbeat_done(void) "enclave heartbeat received"
include/hw/nitro/heartbeat.h
new
+24
@@ -0,0 +1,24 @@
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+/*
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+ * Nitro Heartbeat device
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+ *
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+ * SPDX-License-Identifier: GPL-2.0-or-later
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+ */
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+
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+#ifndef HW_MISC_NITRO_HEARTBEAT_H
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+#define HW_MISC_NITRO_HEARTBEAT_H
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+
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+#include "hw/nitro/nitro-vsock-bus.h"
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+#include "chardev/char-fe.h"
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+#include "qom/object.h"
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+
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+#define TYPE_NITRO_HEARTBEAT "nitro-heartbeat"
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+OBJECT_DECLARE_SIMPLE_TYPE(NitroHeartbeatState, NITRO_HEARTBEAT)
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+
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+struct NitroHeartbeatState {
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+ NitroVsockDevice parent_obj;
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+
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+ CharFrontend vsock; /* vsock server chardev for heartbeat */
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+ bool done;
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+};
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+
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+#endif /* HW_MISC_NITRO_HEARTBEAT_H */