On Sat, Aug 10, 2024 at 10:44:59PM +0600, Dorjoy Chowdhury wrote:
> AWS Nitro Enclaves have built-in vhost-vsock device support which
> enables applications in enclave VMs to communicate with the parent
> EC2 VM over vsock. The enclave VMs have dynamic CID while the parent
> always has CID 3. In QEMU, the vsock emulation for nitro enclave is
> added using vhost-user-vsock as opposed to vhost-vsock. vhost-vsock
> doesn't support sibling VM communication which is needed for nitro
> enclaves.
>
> In QEMU's nitro-enclave emulation, for the vsock communication to CID
> 3 to work, another process that does the vsock emulation in userspace
> must be run, for example, vhost-device-vsock[1] from rust-vmm, with
> necessary vsock communication support in another guest VM with CID 3.
> A new mandatory nitro-enclave machine option 'vsock' has been added.
> The value for this option should be the chardev id from the '-chardev'
> option for the vhost-user-vsock device to work.
>
> Using vhost-user-vsock also enables the possibility to implement some
> proxying support in the vhost-user-vsock daemon that will forward all
> the packets to the host machine instead of CID 3 so that users of
> nitro-enclave can run the necessary applications in their host machine
> instead of running another whole VM with CID 3.
>
> [1] https://github.com/rust-vmm/vhost-device/tree/main/vhost-device-vsock
>
> Signed-off-by: Dorjoy Chowdhury <dorjoychy...@gmail.com>
> ---
> backends/hostmem-memfd.c | 2 -
> hw/core/machine.c | 71 +++++++++---------
> hw/i386/Kconfig | 1 +
> hw/i386/nitro_enclave.c | 123 ++++++++++++++++++++++++++++++++
> include/hw/boards.h | 2 +
> include/hw/i386/nitro_enclave.h | 8 +++
> include/sysemu/hostmem.h | 2 +
> 7 files changed, 174 insertions(+), 35 deletions(-)
>
> diff --git a/hw/i386/nitro_enclave.c b/hw/i386/nitro_enclave.c
> index 98690c6373..280ab4cc9b 100644
> --- a/hw/i386/nitro_enclave.c
> +++ b/hw/i386/nitro_enclave.c
> @@ -11,11 +11,81 @@
> #include "qemu/osdep.h"
> #include "qemu/error-report.h"
> #include "qapi/error.h"
> +#include "qom/object_interfaces.h"
>
> +#include "chardev/char.h"
> +#include "hw/sysbus.h"
> #include "hw/core/eif.h"
> #include "hw/i386/x86.h"
> #include "hw/i386/microvm.h"
> #include "hw/i386/nitro_enclave.h"
> +#include "hw/virtio/virtio-mmio.h"
> +#include "hw/virtio/vhost-user-vsock.h"
> +#include "sysemu/hostmem.h"
> +
> +static BusState *find_free_virtio_mmio_bus(void)
> +{
> + BusChild *kid;
> + BusState *bus = sysbus_get_default();
> +
> + QTAILQ_FOREACH(kid, &bus->children, sibling) {
> + DeviceState *dev = kid->child;
> + if (object_dynamic_cast(OBJECT(dev), TYPE_VIRTIO_MMIO)) {
> + VirtIOMMIOProxy *mmio = VIRTIO_MMIO(OBJECT(dev));
> + VirtioBusState *mmio_virtio_bus = &mmio->bus;
> + BusState *mmio_bus = &mmio_virtio_bus->parent_obj;
> + if (QTAILQ_EMPTY(&mmio_bus->children)) {
> + return mmio_bus;
> + }
> + }
> + }
> +
> + return NULL;
> +}
> +
> +static void vhost_user_vsock_init(NitroEnclaveMachineState *nems)
> +{
> + DeviceState *dev = qdev_new(TYPE_VHOST_USER_VSOCK);
> + VHostUserVSock *vsock = VHOST_USER_VSOCK(dev);
> + BusState *bus;
> +
> + if (!nems->vsock) {
> + error_report("A valid chardev id for vhost-user-vsock device must be
> "
> + "provided using the 'vsock' machine option");
> + exit(1);
> + }
> +
> + bus = find_free_virtio_mmio_bus();
> + if (!bus) {
> + error_report("Failed to find bus for vhost-user-vsock device");
> + exit(1);
> + }
> +
> + Chardev *chardev = qemu_chr_find(nems->vsock);
> + if (!chardev) {
> + error_report("Failed to find chardev with id %s", nems->vsock);
> + exit(1);
> + }
> +
> + vsock->conf.chardev.chr = chardev;
> +
> + qdev_realize_and_unref(dev, bus, &error_fatal);
> +}
Why does this machine need to create the vhost-user-vsock device itself ?
Doing it this way prevents the mgmt app from changing any of the other
vsock device settings beyond 'chardev'. The entity creating QEMU can use
-device to create the vsock device.
> +
> +static void nitro_enclave_devices_init(NitroEnclaveMachineState *nems)
> +{
> + vhost_user_vsock_init(nems);
> +}
> +
> +static void nitro_enclave_machine_state_init(MachineState *machine)
> +{
> + NitroEnclaveMachineClass *ne_class =
> + NITRO_ENCLAVE_MACHINE_GET_CLASS(machine);
> + NitroEnclaveMachineState *ne_state = NITRO_ENCLAVE_MACHINE(machine);
> +
> + ne_class->parent_init(machine);
> + nitro_enclave_devices_init(ne_state);
> +}
>
> static void nitro_enclave_machine_initfn(Object *obj)
> {
> @@ -66,15 +136,68 @@ static void x86_load_eif(X86MachineState *x86ms,
> FWCfgState *fw_cfg,
> return;
> }
>
> +static bool create_memfd_backend(MachineState *ms, const char *path,
> + Error **errp)
> +{
> + Object *obj;
> + MachineClass *mc = MACHINE_GET_CLASS(ms);
> + bool r = false;
> +
> + obj = object_new(TYPE_MEMORY_BACKEND_MEMFD);
> + if (!object_property_set_int(obj, "size", ms->ram_size, errp)) {
> + goto out;
> + }
> + object_property_add_child(object_get_objects_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 char *nitro_enclave_get_vsock_chardev_id(Object *obj, Error **errp)
> +{
> + NitroEnclaveMachineState *nems = NITRO_ENCLAVE_MACHINE(obj);
> +
> + return g_strdup(nems->vsock);
> +}
> +
> +static void nitro_enclave_set_vsock_chardev_id(Object *obj, const char
> *value,
> + Error **errp)
> +{
> + NitroEnclaveMachineState *nems = NITRO_ENCLAVE_MACHINE(obj);
> +
> + g_free(nems->vsock);
> + nems->vsock = g_strdup(value);
> +}
> +
> static void nitro_enclave_class_init(ObjectClass *oc, void *data)
> {
> MachineClass *mc = MACHINE_CLASS(oc);
> MicrovmMachineClass *mmc = MICROVM_MACHINE_CLASS(oc);
> + NitroEnclaveMachineClass *nemc = NITRO_ENCLAVE_MACHINE_CLASS(oc);
>
> mmc->x86_load_linux = x86_load_eif;
>
> mc->family = "nitro_enclave_i386";
> mc->desc = "AWS Nitro Enclave";
> +
> + nemc->parent_init = mc->init;
> + mc->init = nitro_enclave_machine_state_init;
> +
> + mc->create_default_memdev = create_memfd_backend;
> +
> + object_class_property_add_str(oc, NITRO_ENCLAVE_VSOCK_CHARDEV_ID,
> + nitro_enclave_get_vsock_chardev_id,
> + nitro_enclave_set_vsock_chardev_id);
> + object_class_property_set_description(oc, NITRO_ENCLAVE_VSOCK_CHARDEV_ID,
> + "Set chardev id for
> vhost-user-vsock "
> + "device");
> }
>
> static const TypeInfo nitro_enclave_machine_info = {
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 48ff6d8b93..c268e7f005 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -308,6 +308,8 @@ struct MachineClass {
> int64_t (*get_default_cpu_node_id)(const MachineState *ms, int idx);
> ram_addr_t (*fixup_ram_size)(ram_addr_t size);
> uint64_t smbios_memory_device_size;
> + bool (*create_default_memdev)(MachineState *ms, const char *path,
> + Error **errp);
> };
>
> /**
> diff --git a/include/hw/i386/nitro_enclave.h b/include/hw/i386/nitro_enclave.h
> index a1dada9371..3e302de851 100644
> --- a/include/hw/i386/nitro_enclave.h
> +++ b/include/hw/i386/nitro_enclave.h
> @@ -14,12 +14,20 @@
> #include "hw/i386/microvm.h"
> #include "qom/object.h"
>
> +/* Machine type options */
> +#define NITRO_ENCLAVE_VSOCK_CHARDEV_ID "vsock"
> +
> struct NitroEnclaveMachineClass {
> MicrovmMachineClass parent;
> +
> + void (*parent_init)(MachineState *state);
> };
>
> struct NitroEnclaveMachineState {
> MicrovmMachineState parent;
> +
> + /* Machine type options */
> + char *vsock;
> };
>
> #define TYPE_NITRO_ENCLAVE_MACHINE MACHINE_TYPE_NAME("nitro-enclave")
> diff --git a/include/sysemu/hostmem.h b/include/sysemu/hostmem.h
> index de47ae59e4..67f45abe39 100644
> --- a/include/sysemu/hostmem.h
> +++ b/include/sysemu/hostmem.h
> @@ -39,6 +39,8 @@ OBJECT_DECLARE_TYPE(HostMemoryBackend,
> HostMemoryBackendClass,
> */
> #define TYPE_MEMORY_BACKEND_FILE "memory-backend-file"
>
> +#define TYPE_MEMORY_BACKEND_MEMFD "memory-backend-memfd"
> +
>
> /**
> * HostMemoryBackendClass:
> --
> 2.39.2
>
With regards,
Daniel
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