Re: [PATCH 07/10] hw/nitro: Add nitro machine

["Michael S. Tsirkin" <mst@redhat.com>]

On Wed, Feb 18, 2026 at 01:51:47AM +0000, Alexander Graf wrote:
> Add a machine model to spawn a Nitro Enclave. Unlike the existing -M
> nitro-enclave, this machine model works exclusively with the -accel
> nitro accelerator to drive real Nitro Enclave creation. It supports
> memory allocation, number of CPU selection, both x86_64 as well as
> aarch64, implements the Enclave heartbeat logic and debug serial
> console.
> 
> To use it, create an EIF file and run
> 
>   $ qemu-system-x86_64 -accel nitro,debug-mode=on -M nitro -nographic \
>                        -kernel test.eif
> 
> or
> 
>   $ qemu-system-aarch64 -accel nitro,debug-mode=on -M nitro -nographic \
>                        -kernel test.eif
> 
> Signed-off-by: Alexander Graf <graf@amazon.com>
> ---
>  hw/nitro/Kconfig           |   7 ++
>  hw/nitro/machine.c         | 180 +++++++++++++++++++++++++++++++++++++
>  hw/nitro/meson.build       |   1 +
>  include/hw/nitro/machine.h |  20 +++++
>  4 files changed, 208 insertions(+)
>  create mode 100644 hw/nitro/machine.c
>  create mode 100644 include/hw/nitro/machine.h
> 
> diff --git a/hw/nitro/Kconfig b/hw/nitro/Kconfig
> index 6fe050d35d..910068c23c 100644
> --- a/hw/nitro/Kconfig
> +++ b/hw/nitro/Kconfig
> @@ -5,3 +5,10 @@ config NITRO_SERIAL_VSOCK
>  config NITRO_HEARTBEAT
>      bool
>      depends on NITRO
> +
> +config NITRO_MACHINE
> +    bool
> +    default y
> +    depends on NITRO
> +    select NITRO_HEARTBEAT
> +    select NITRO_SERIAL_VSOCK
> diff --git a/hw/nitro/machine.c b/hw/nitro/machine.c
> new file mode 100644
> index 0000000000..197adfbdb5
> --- /dev/null
> +++ b/hw/nitro/machine.c
> @@ -0,0 +1,180 @@
> +/*
> + * Nitro Enclaves (accel) machine
> + *
> + * Copyright © 2026 Amazon.com, Inc. or its affiliates. All Rights Reserved.
> + *
> + * Authors:
> + *   Alexander Graf <graf@amazon.com>
> + *
> + * Nitro Enclaves machine model for -accel nitro. This machine behaves
> + * like the nitro-enclave machine, but uses the real Nitro Enclaves
> + * backend to launch the virtual machine. It requires use of the -accel
> + * nitro.
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/error-report.h"
> +#include "qapi/error.h"
> +#include "qom/object_interfaces.h"
> +#include "chardev/char.h"
> +#include "hw/core/boards.h"
> +#include "hw/core/cpu.h"
> +#include "hw/core/sysbus.h"
> +#include "hw/core/qdev-properties-system.h"
> +#include "hw/nitro/heartbeat.h"
> +#include "hw/nitro/machine.h"
> +#include "hw/nitro/serial-vsock.h"
> +#include "system/address-spaces.h"
> +#include "system/hostmem.h"
> +#include "system/system.h"
> +#include "system/nitro-accel.h"
> +#include "qemu/accel.h"
> +#include "hw/arm/machines-qom.h"
> +
> +#define EIF_LOAD_ADDR   (8 * 1024 * 1024)
> +
> +static void nitro_create_cpu(const char *cpu_type, int index)
> +{
> +    Object *obj = object_new(cpu_type);
> +
> +    /* x86 CPUs require an apic-id before realize */
> +    if (object_property_find(obj, "apic-id")) {
> +        object_property_set_int(obj, "apic-id", index, &error_fatal);
> +    }
> +
> +    qdev_realize(DEVICE(obj), NULL, &error_fatal);
> +}
> +
> +static void nitro_machine_init(MachineState *machine)
> +{
> +    const char *eif_path = machine->kernel_filename;
> +    const char *cpu_type = machine->cpu_type;
> +    g_autofree char *eif_data = NULL;
> +    gsize eif_size;
> +    int i;
> +
> +    if (!nitro_enabled()) {
> +        error_report("The 'nitro' machine requires -accel nitro");
> +        exit(1);
> +    }
> +
> +    if (!cpu_type) {
> +        ObjectClass *oc = cpu_class_by_name(target_cpu_type(), "host");
> +
> +        if (!oc) {
> +            error_report("nitro: no 'host' CPU available");
> +            exit(1);
> +        }
> +        cpu_type = object_class_get_name(oc);
> +    }
> +
> +    if (!eif_path) {
> +        error_report("nitro: -kernel <eif-file> is required");
> +        exit(1);
> +    }
> +
> +    /* Expose memory as normal QEMU RAM. Needs to be huge page backed. */
> +    memory_region_add_subregion(get_system_memory(), 0, machine->ram);
> +
> +    /*
> +     * Load EIF (-kernel) as raw blob at the EIF_LOAD_ADDR into guest RAM.
> +     * The Nitro Hypervisor will extract its contents and bootstrap the
> +     * Enclave from it.
> +     */
> +    if (!g_file_get_contents(eif_path, &eif_data, &eif_size, NULL)) {
> +        error_report("nitro: failed to read EIF '%s'", eif_path);
> +        exit(1);
> +    }
> +    address_space_write(&address_space_memory, EIF_LOAD_ADDR,
> +                        MEMTXATTRS_UNSPECIFIED, eif_data, eif_size);
> +
> +    /* Nitro Enclaves require a heartbeat device. Provide one. */
> +    sysbus_realize_and_unref(SYS_BUS_DEVICE(qdev_new(TYPE_NITRO_HEARTBEAT)),
> +                             &error_fatal);
> +
> +    /*
> +     * In debug mode, Nitro Enclaves expose the guest's serial output via
> +     * vsock. When the accel is in debug mode, wire the vsock serial to
> +     * the machine's serial port so that -nographic automatically works
> +     */
> +    if (object_property_get_bool(OBJECT(current_accel()), "debug-mode", NULL)) {
> +        Chardev *chr = serial_hd(0);
> +
> +        if (chr) {
> +            DeviceState *dev = qdev_new(TYPE_NITRO_SERIAL_VSOCK);
> +
> +            qdev_prop_set_chr(dev, "chardev", chr);
> +            sysbus_realize_and_unref(SYS_BUS_DEVICE(dev), &error_fatal);
> +        }
> +    }


Would  respecting -nodefaults and then maybe not wiring up all the
vsock things make sense? allows users to set it up any way
they want ...

> +
> +    /*
> +     * Spawn vCPUs. While the real Nitro Enclaves CPUs are owned by the
> +     * underlying hypervisor, we still want to maintain a local view of
> +     * them to trigger VM creation when vCPU 0 starts and to give us an
> +     * object to interact with.
> +     */
> +    for (i = 0; i < machine->smp.cpus; i++) {
> +        nitro_create_cpu(cpu_type, i);
> +    }
> +}
> +
> +static bool nitro_create_memfd_backend(MachineState *ms, const char *path,
> +                                       Error **errp)
> +{
> +    MachineClass *mc = MACHINE_GET_CLASS(ms);
> +    Object *root = object_get_objects_root();
> +    Object *obj;
> +    bool r = false;
> +
> +    obj = object_new(TYPE_MEMORY_BACKEND_MEMFD);
> +
> +    /* Nitro Enclaves require huge page backing */
> +    if (!object_property_set_int(obj, "size", ms->ram_size, errp) ||
> +        !object_property_set_bool(obj, "hugetlb", true, errp)) {
> +        goto out;
> +    }
> +
> +    object_property_add_child(root, mc->default_ram_id, obj);
> +
> +    if (!user_creatable_complete(USER_CREATABLE(obj), errp)) {
> +        goto out;
> +    }
> +    r = object_property_set_link(OBJECT(ms), "memory-backend", obj, errp);
> +
> +out:
> +    object_unref(obj);
> +    return r;
> +}
> +
> +static void nitro_machine_class_init(ObjectClass *oc, const void *data)
> +{
> +    MachineClass *mc = MACHINE_CLASS(oc);
> +
> +    mc->desc = "Nitro Enclave";
> +    mc->init = nitro_machine_init;
> +    mc->create_default_memdev = nitro_create_memfd_backend;
> +    mc->default_ram_id = "ram";
> +    mc->max_cpus = 4096;
> +}
> +
> +static const TypeInfo nitro_machine_info = {
> +    .name = TYPE_NITRO_MACHINE,
> +    .parent = TYPE_MACHINE,
> +    .instance_size = sizeof(NitroMachineState),
> +    .class_init = nitro_machine_class_init,
> +    .interfaces = (const InterfaceInfo[]) {
> +        /* x86_64 and aarch64 only */
> +        { TYPE_TARGET_AARCH64_MACHINE },
> +        { }
> +    },
> +};
> +
> +static void nitro_machine_register(void)
> +{
> +    type_register_static(&nitro_machine_info);
> +}
> +
> +type_init(nitro_machine_register);
> diff --git a/hw/nitro/meson.build b/hw/nitro/meson.build
> index b921da2b97..813f5a9c87 100644
> --- a/hw/nitro/meson.build
> +++ b/hw/nitro/meson.build
> @@ -1,2 +1,3 @@
>  system_ss.add(when: 'CONFIG_NITRO_SERIAL_VSOCK', if_true: files('serial-vsock.c'))
>  system_ss.add(when: 'CONFIG_NITRO_HEARTBEAT', if_true: files('heartbeat.c'))
> +system_ss.add(when: 'CONFIG_NITRO_MACHINE', if_true: files('machine.c'))
> diff --git a/include/hw/nitro/machine.h b/include/hw/nitro/machine.h
> new file mode 100644
> index 0000000000..d78ba7d6dc
> --- /dev/null
> +++ b/include/hw/nitro/machine.h
> @@ -0,0 +1,20 @@
> +/*
> + * Nitro Enclaves (accel) machine
> + *
> + * SPDX-License-Identifier: GPL-2.0-or-later
> + */
> +
> +#ifndef HW_NITRO_MACHINE_H
> +#define HW_NITRO_MACHINE_H
> +
> +#include "hw/core/boards.h"
> +#include "qom/object.h"
> +
> +#define TYPE_NITRO_MACHINE MACHINE_TYPE_NAME("nitro")
> +OBJECT_DECLARE_SIMPLE_TYPE(NitroMachineState, NITRO_MACHINE)
> +
> +struct NitroMachineState {
> +    MachineState parent;
> +};
> +
> +#endif /* HW_NITRO_MACHINE_H */
> -- 
> 2.47.1
> 
> 
> 
> 
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