Re: [PATCH v4 8/8] hw/i386: Introduce the microvm machine type

[Philippe Mathieu-Daudé]

On 9/24/19 2:44 PM, Sergio Lopez wrote:
> Microvm is a machine type inspired by both NEMU and Firecracker, and
> constructed after the machine model implemented by the latter.
> 
> It's main purpose is providing users a minimalist machine type free
> from the burden of legacy compatibility, serving as a stepping stone
> for future projects aiming at improving boot times, reducing the
> attack surface and slimming down QEMU's footprint.
> 
> The microvm machine type supports the following devices:
> 
>  - ISA bus
>  - i8259 PIC
>  - LAPIC (implicit if using KVM)
>  - IOAPIC (defaults to kernel_irqchip_split = true)
>  - i8254 PIT
>  - MC146818 RTC (optional)
>  - kvmclock (if using KVM)
>  - fw_cfg
>  - One ISA serial port (optional)
>  - Up to eight virtio-mmio devices (configured by the user)
> 
> It supports the following machine-specific options:
> 
> microvm.option-roms=bool (Set off to disable loading option ROMs)
> microvm.isa-serial=bool (Set off to disable the instantiation an ISA serial 
> port)
> microvm.rtc=bool (Set off to disable the instantiation of an MC146818 RTC)
> microvm.kernel-cmdline=bool (Set off to disable adding virtio-mmio devices to 
> the kernel cmdline)
> 
> By default, microvm uses qboot as its BIOS, to obtain better boot
> times, but it's also compatible with SeaBIOS.
> 
> As no current FW is able to boot from a block device using virtio-mmio
> as its transport, a microvm-based VM needs to be run using a host-side
> kernel and, optionally, an initrd image.
> 
> This is an example of instantiating a microvm VM with a virtio-mmio
> based console:
> 
> qemu-system-x86_64 -M microvm
>  -enable-kvm -cpu host -m 512m -smp 2 \
>  -kernel vmlinux -append "console=hvc0 root=/dev/vda" \
>  -nodefaults -no-user-config -nographic \
>  -chardev stdio,id=virtiocon0,server \
>  -device virtio-serial-device \
>  -device virtconsole,chardev=virtiocon0 \
>  -drive id=test,file=test.img,format=raw,if=none \
>  -device virtio-blk-device,drive=test \
>  -netdev tap,id=tap0,script=no,downscript=no \
>  -device virtio-net-device,netdev=tap0
> 
> This is another example, this time using an ISA serial port, useful
> for debugging purposes:
> 
> qemu-system-x86_64 -M microvm \
>  -enable-kvm -cpu host -m 512m -smp 2 \
>  -kernel vmlinux -append "earlyprintk=ttyS0 console=ttyS0 root=/dev/vda" \
>  -nodefaults -no-user-config -nographic \
>  -serial stdio \
>  -drive id=test,file=test.img,format=raw,if=none \
>  -device virtio-blk-device,drive=test \
>  -netdev tap,id=tap0,script=no,downscript=no \
>  -device virtio-net-device,netdev=tap0
> 
> Finally, in this example a microvm VM is instantiated without RTC,
> without an ISA serial port and without loading the option ROMs,
> obtaining the smallest configuration:
> 
> qemu-system-x86_64 -M microvm,rtc=off,isa-serial=off,option-roms=off \
>  -enable-kvm -cpu host -m 512m -smp 2 \
>  -kernel vmlinux -append "console=hvc0 root=/dev/vda" \
>  -nodefaults -no-user-config -nographic \
>  -chardev stdio,id=virtiocon0,server \
>  -device virtio-serial-device \
>  -device virtconsole,chardev=virtiocon0 \
>  -drive id=test,file=test.img,format=raw,if=none \
>  -device virtio-blk-device,drive=test \
>  -netdev tap,id=tap0,script=no,downscript=no \
>  -device virtio-net-device,netdev=tap0
> 
> Signed-off-by: Sergio Lopez <address@hidden>
> ---
>  default-configs/i386-softmmu.mak |   1 +
>  hw/i386/Kconfig                  |   4 +
>  hw/i386/Makefile.objs            |   1 +
>  hw/i386/microvm.c                | 512 +++++++++++++++++++++++++++++++
>  include/hw/i386/microvm.h        |  80 +++++
>  5 files changed, 598 insertions(+)
>  create mode 100644 hw/i386/microvm.c
>  create mode 100644 include/hw/i386/microvm.h
> 
> diff --git a/default-configs/i386-softmmu.mak 
> b/default-configs/i386-softmmu.mak
> index cd5ea391e8..c27cdd98e9 100644
> --- a/default-configs/i386-softmmu.mak
> +++ b/default-configs/i386-softmmu.mak
> @@ -26,3 +26,4 @@ CONFIG_ISAPC=y
>  CONFIG_I440FX=y
>  CONFIG_Q35=y
>  CONFIG_ACPI_PCI=y
> +CONFIG_MICROVM=y
> \ No newline at end of file
> diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
> index 6350438036..324e193dd8 100644
> --- a/hw/i386/Kconfig
> +++ b/hw/i386/Kconfig
> @@ -88,6 +88,10 @@ config Q35
>      select SMBIOS
>      select FW_CFG_DMA
>  
> +config MICROVM
> +    bool
> +    select VIRTIO_MMIO
> +
>  config VTD
>      bool
>  
> diff --git a/hw/i386/Makefile.objs b/hw/i386/Makefile.objs
> index 5b4b3a672e..bb17d54567 100644
> --- a/hw/i386/Makefile.objs
> +++ b/hw/i386/Makefile.objs
> @@ -6,6 +6,7 @@ obj-y += pc.o
>  obj-y += e820.o
>  obj-$(CONFIG_I440FX) += pc_piix.o
>  obj-$(CONFIG_Q35) += pc_q35.o
> +obj-$(CONFIG_MICROVM) += microvm.o
>  obj-y += fw_cfg.o pc_sysfw.o
>  obj-y += x86-iommu.o
>  obj-$(CONFIG_VTD) += intel_iommu.o
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> new file mode 100644
> index 0000000000..4b494a1b27
> --- /dev/null
> +++ b/hw/i386/microvm.c
> @@ -0,0 +1,512 @@
> +/*
> + * Copyright (c) 2018 Intel Corporation
> + * Copyright (c) 2019 Red Hat, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include "qemu/osdep.h"
> +#include "qemu/error-report.h"
> +#include "qemu/cutils.h"
> +#include "qemu/units.h"
> +#include "qapi/error.h"
> +#include "qapi/visitor.h"
> +#include "sysemu/sysemu.h"
> +#include "sysemu/cpus.h"
> +#include "sysemu/numa.h"
> +#include "sysemu/reset.h"
> +
> +#include "hw/loader.h"
> +#include "hw/irq.h"
> +#include "hw/nmi.h"
> +#include "hw/kvm/clock.h"
> +#include "hw/i386/microvm.h"
> +#include "hw/i386/x86.h"
> +#include "hw/i386/pc.h"
> +#include "target/i386/cpu.h"
> +#include "hw/timer/i8254.h"
> +#include "hw/timer/mc146818rtc.h"
> +#include "hw/char/serial.h"
> +#include "hw/i386/topology.h"
> +#include "hw/i386/e820.h"
> +#include "hw/i386/fw_cfg.h"
> +#include "hw/virtio/virtio-mmio.h"
> +
> +#include "cpu.h"
> +#include "elf.h"
> +#include "pvh.h"
> +#include "kvm_i386.h"
> +#include "hw/xen/start_info.h"
> +
> +#define MICROVM_BIOS_FILENAME "bios-microvm.bin"
> +
> +static void microvm_set_rtc(MicrovmMachineState *mms, ISADevice *s)
> +{
> +    X86MachineState *x86ms = X86_MACHINE(mms);
> +    int val;
> +
> +    val = MIN(x86ms->below_4g_mem_size / KiB, 640);
> +    rtc_set_memory(s, 0x15, val);
> +    rtc_set_memory(s, 0x16, val >> 8);
> +    /* extended memory (next 64MiB) */
> +    if (x86ms->below_4g_mem_size > 1 * MiB) {
> +        val = (x86ms->below_4g_mem_size - 1 * MiB) / KiB;
> +    } else {
> +        val = 0;
> +    }
> +    if (val > 65535) {
> +        val = 65535;
> +    }
> +    rtc_set_memory(s, 0x17, val);
> +    rtc_set_memory(s, 0x18, val >> 8);
> +    rtc_set_memory(s, 0x30, val);
> +    rtc_set_memory(s, 0x31, val >> 8);
> +    /* memory between 16MiB and 4GiB */
> +    if (x86ms->below_4g_mem_size > 16 * MiB) {
> +        val = (x86ms->below_4g_mem_size - 16 * MiB) / (64 * KiB);
> +    } else {
> +        val = 0;
> +    }
> +    if (val > 65535) {
> +        val = 65535;
> +    }
> +    rtc_set_memory(s, 0x34, val);
> +    rtc_set_memory(s, 0x35, val >> 8);
> +    /* memory above 4GiB */
> +    val = x86ms->above_4g_mem_size / 65536;
> +    rtc_set_memory(s, 0x5b, val);
> +    rtc_set_memory(s, 0x5c, val >> 8);
> +    rtc_set_memory(s, 0x5d, val >> 16);
> +}
> +
> +static void microvm_devices_init(MicrovmMachineState *mms)
> +{
> +    X86MachineState *x86ms = X86_MACHINE(mms);
> +    ISABus *isa_bus;
> +    ISADevice *rtc_state;
> +    GSIState *gsi_state;
> +    qemu_irq *i8259;
> +    int i;
> +
> +    gsi_state = g_malloc0(sizeof(*gsi_state));
> +    x86ms->gsi = qemu_allocate_irqs(gsi_handler, gsi_state, GSI_NUM_PINS);
> +
> +    isa_bus = isa_bus_new(NULL, get_system_memory(), get_system_io(),
> +                          &error_abort);
> +    isa_bus_irqs(isa_bus, x86ms->gsi);
> +
> +    i8259 = i8259_init(isa_bus, pc_allocate_cpu_irq());
> +
> +    for (i = 0; i < ISA_NUM_IRQS; i++) {
> +        gsi_state->i8259_irq[i] = i8259[i];
> +    }
> +
> +    ioapic_init_gsi(gsi_state, "machine");
> +
> +    if (mms->rtc_enabled) {
> +        rtc_state = mc146818_rtc_init(isa_bus, 2000, NULL);
> +        microvm_set_rtc(mms, rtc_state);
> +    }
> +

Maybe refactor that ...

> +    if (kvm_pit_in_kernel()) {
> +        kvm_pit_init(isa_bus, 0x40);
> +    } else {
> +        i8254_pit_init(isa_bus, 0x40, 0, NULL);
> +    }

... as a x86_pit_create() function?

> +
> +    kvmclock_create();
> +
> +    for (i = 0; i < VIRTIO_NUM_TRANSPORTS; i++) {
> +        int nirq = VIRTIO_IRQ_BASE + i;
> +        ISADevice *isadev = isa_create(isa_bus, TYPE_ISA_SERIAL);
> +        qemu_irq mmio_irq;
> +
> +        isa_init_irq(isadev, &mmio_irq, nirq);
> +        sysbus_create_simple("virtio-mmio",
> +                             VIRTIO_MMIO_BASE + i * 512,
> +                             x86ms->gsi[VIRTIO_IRQ_BASE + i]);
> +    }
> +
> +    g_free(i8259);

Not related to this patch, but i8259_init() API is not clear,
it returns an allocated array of allocated qemu_irqs? Is it safe to copy
them to gsi_state then free the array?

> +
> +    if (mms->isa_serial_enabled) {
> +        serial_hds_isa_init(isa_bus, 0, 1);
> +    }
> +
> +    if (bios_name == NULL) {
> +        bios_name = MICROVM_BIOS_FILENAME;
> +    }
> +    x86_system_rom_init(get_system_memory(), true);
> +}
> +
> +static void microvm_memory_init(MicrovmMachineState *mms)
> +{
> +    MachineState *machine = MACHINE(mms);
> +    X86MachineState *x86ms = X86_MACHINE(mms);
> +    MemoryRegion *ram, *ram_below_4g, *ram_above_4g;
> +    MemoryRegion *system_memory = get_system_memory();
> +    FWCfgState *fw_cfg;
> +    ram_addr_t lowmem;
> +    int i;
> +
> +    /*
> +     * Check whether RAM fits below 4G (leaving 1/2 GByte for IO memory
> +     * and 256 Mbytes for PCI Express Enhanced Configuration Access Mapping
> +     * also known as MMCFG).
> +     * If it doesn't, we need to split it in chunks below and above 4G.
> +     * In any case, try to make sure that guest addresses aligned at
> +     * 1G boundaries get mapped to host addresses aligned at 1G boundaries.
> +     */
> +    if (machine->ram_size >= 0xb0000000) {
> +        lowmem = 0x80000000;
> +    } else {
> +        lowmem = 0xb0000000;
> +    }
> +
> +    /*
> +     * Handle the machine opt max-ram-below-4g.  It is basically doing
> +     * min(qemu limit, user limit).
> +     */
> +    if (!x86ms->max_ram_below_4g) {
> +        x86ms->max_ram_below_4g = 1ULL << 32; /* default: 4G */

Please use '4 * GiB' with no comment.

> +    }
> +    if (lowmem > x86ms->max_ram_below_4g) {
> +        lowmem = x86ms->max_ram_below_4g;
> +        if (machine->ram_size - lowmem > lowmem &&
> +            lowmem & (1 * GiB - 1)) {
> +            warn_report("There is possibly poor performance as the ram size "
> +                        " (0x%" PRIx64 ") is more then twice the size of"
> +                        " max-ram-below-4g (%"PRIu64") and"
> +                        " max-ram-below-4g is not a multiple of 1G.",
> +                        (uint64_t)machine->ram_size, 
> x86ms->max_ram_below_4g);
> +        }
> +    }
> +
> +    if (machine->ram_size > lowmem) {
> +        x86ms->above_4g_mem_size = machine->ram_size - lowmem;
> +        x86ms->below_4g_mem_size = lowmem;
> +    } else {
> +        x86ms->above_4g_mem_size = 0;
> +        x86ms->below_4g_mem_size = machine->ram_size;
> +    }
> +
> +    ram = g_malloc(sizeof(*ram));
> +    memory_region_allocate_system_memory(ram, NULL, "microvm.ram",
> +                                         machine->ram_size);
> +
> +    ram_below_4g = g_malloc(sizeof(*ram_below_4g));
> +    memory_region_init_alias(ram_below_4g, NULL, "ram-below-4g", ram,
> +                             0, x86ms->below_4g_mem_size);
> +    memory_region_add_subregion(system_memory, 0, ram_below_4g);
> +
> +    e820_add_entry(0, x86ms->below_4g_mem_size, E820_RAM);
> +
> +    if (x86ms->above_4g_mem_size > 0) {
> +        ram_above_4g = g_malloc(sizeof(*ram_above_4g));
> +        memory_region_init_alias(ram_above_4g, NULL, "ram-above-4g", ram,
> +                                 x86ms->below_4g_mem_size,
> +                                 x86ms->above_4g_mem_size);
> +        memory_region_add_subregion(system_memory, 0x100000000ULL,
> +                                    ram_above_4g);
> +        e820_add_entry(0x100000000ULL, x86ms->above_4g_mem_size, E820_RAM);
> +    }
> +
> +    fw_cfg = fw_cfg_init_io_dma(FW_CFG_IO_BASE, FW_CFG_IO_BASE + 4,
> +                                &address_space_memory);
> +
> +    fw_cfg_add_i16(fw_cfg, FW_CFG_NB_CPUS, x86ms->boot_cpus);
> +    fw_cfg_add_i16(fw_cfg, FW_CFG_MAX_CPUS, (uint16_t)x86ms->apic_id_limit);
> +    fw_cfg_add_i64(fw_cfg, FW_CFG_RAM_SIZE, (uint64_t)machine->ram_size);
> +    fw_cfg_add_i32(fw_cfg, FW_CFG_IRQ0_OVERRIDE, kvm_allows_irq0_override());
> +
> +    rom_set_fw(fw_cfg);
> +
> +    e820_create_fw_entry(fw_cfg);
> +
> +    load_linux(x86ms, fw_cfg, 0, true, true);
> +
> +    if (mms->option_roms_enabled) {
> +        for (i = 0; i < nb_option_roms; i++) {
> +            rom_add_option(option_rom[i].name, option_rom[i].bootindex);
> +        }
> +    }
> +
> +    x86ms->fw_cfg = fw_cfg;
> +    x86ms->ioapic_as = &address_space_memory;
> +}
> +
> +static gchar *microvm_get_mmio_cmdline(gchar *name)
> +{
> +    gchar *cmdline;
> +    gchar *separator;
> +    long int index;
> +    int ret;
> +
> +    separator = g_strrstr(name, ".");
> +    if (!separator) {
> +        return NULL;
> +    }
> +
> +    if (qemu_strtol(separator + 1, NULL, 10, &index) != 0) {
> +        return NULL;
> +    }
> +
> +    cmdline = g_malloc0(VIRTIO_CMDLINE_MAXLEN);
> +    ret = g_snprintf(cmdline, VIRTIO_CMDLINE_MAXLEN,
> +                     " virtio_mmio.device=512@0x%lx:%ld",
> +                     VIRTIO_MMIO_BASE + index * 512,
> +                     VIRTIO_IRQ_BASE + index);
> +    if (ret < 0 || ret >= VIRTIO_CMDLINE_MAXLEN) {
> +        g_free(cmdline);
> +        return NULL;
> +    }
> +
> +    return cmdline;
> +}
> +
> +static void microvm_fix_kernel_cmdline(MachineState *machine)
> +{
> +    X86MachineState *x86ms = X86_MACHINE(machine);
> +    BusState *bus;
> +    BusChild *kid;
> +    char *cmdline;
> +
> +    /*
> +     * Find MMIO transports with attached devices, and add them to the kernel
> +     * command line.
> +     *
> +     * Yes, this is a hack, but one that heavily improves the UX without
> +     * introducing any significant issues.
> +     */
> +    cmdline = g_strdup(machine->kernel_cmdline);
> +    bus = sysbus_get_default();
> +    QTAILQ_FOREACH(kid, &bus->children, sibling) {
> +        DeviceState *dev = kid->child;
> +        ObjectClass *class = object_get_class(OBJECT(dev));
> +
> +        if (class == object_class_by_name(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)) {
> +                gchar *mmio_cmdline = 
> microvm_get_mmio_cmdline(mmio_bus->name);
> +                if (mmio_cmdline) {
> +                    char *newcmd = g_strjoin(NULL, cmdline, mmio_cmdline, 
> NULL);
> +                    g_free(mmio_cmdline);
> +                    g_free(cmdline);
> +                    cmdline = newcmd;
> +                }
> +            }
> +        }
> +    }
> +
> +    fw_cfg_modify_i32(x86ms->fw_cfg, FW_CFG_CMDLINE_SIZE, strlen(cmdline) + 
> 1);
> +    fw_cfg_modify_string(x86ms->fw_cfg, FW_CFG_CMDLINE_DATA, cmdline);
> +}
> +
> +static void microvm_machine_state_init(MachineState *machine)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(machine);
> +    X86MachineState *x86ms = X86_MACHINE(machine);
> +    Error *local_err = NULL;
> +
> +    if (machine->kernel_filename == NULL) {
> +        error_report("missing kernel image file name, required by microvm");
> +        exit(1);
> +    }
> +
> +    microvm_memory_init(mms);
> +
> +    x86_cpus_init(x86ms, CPU_VERSION_LATEST);
> +    if (local_err) {
> +        error_report_err(local_err);
> +        exit(1);
> +    }
> +
> +    microvm_devices_init(mms);
> +}
> +
> +static void microvm_machine_reset(MachineState *machine)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(machine);
> +    CPUState *cs;
> +    X86CPU *cpu;
> +
> +    if (mms->kernel_cmdline_enabled && !mms->kernel_cmdline_fixed) {
> +        microvm_fix_kernel_cmdline(machine);
> +        mms->kernel_cmdline_fixed = true;
> +    }
> +
> +    qemu_devices_reset();
> +
> +    CPU_FOREACH(cs) {
> +        cpu = X86_CPU(cs);
> +
> +        if (cpu->apic_state) {
> +            device_reset(cpu->apic_state);
> +        }
> +    }
> +}
> +
> +static bool microvm_machine_get_rtc(Object *obj, Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    return mms->rtc_enabled;
> +}
> +
> +static void microvm_machine_set_rtc(Object *obj, bool value, Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    mms->rtc_enabled = value;
> +}
> +
> +static bool microvm_machine_get_isa_serial(Object *obj, Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    return mms->isa_serial_enabled;
> +}
> +
> +static void microvm_machine_set_isa_serial(Object *obj, bool value,
> +                                           Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    mms->isa_serial_enabled = value;
> +}
> +
> +static bool microvm_machine_get_option_roms(Object *obj, Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    return mms->option_roms_enabled;
> +}
> +
> +static void microvm_machine_set_option_roms(Object *obj, bool value,
> +                                            Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    mms->option_roms_enabled = value;
> +}
> +
> +static bool microvm_machine_get_kernel_cmdline(Object *obj, Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    return mms->kernel_cmdline_enabled;
> +}
> +
> +static void microvm_machine_set_kernel_cmdline(Object *obj, bool value,
> +                                               Error **errp)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    mms->kernel_cmdline_enabled = value;
> +}
> +
> +static void microvm_machine_initfn(Object *obj)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(obj);
> +
> +    /* Configuration */
> +    mms->rtc_enabled = true;
> +    mms->isa_serial_enabled = true;
> +    mms->option_roms_enabled = true;
> +    mms->kernel_cmdline_enabled = true;
> +
> +    /* State */
> +    mms->kernel_cmdline_fixed = false;
> +}
> +
> +static void microvm_class_init(ObjectClass *oc, void *data)
> +{
> +    MachineClass *mc = MACHINE_CLASS(oc);
> +    NMIClass *nc = NMI_CLASS(oc);
> +
> +    mc->init = microvm_machine_state_init;
> +
> +    mc->family = "microvm_i386";
> +    mc->desc = "Microvm (i386)";
> +    mc->units_per_default_bus = 1;
> +    mc->no_floppy = 1;
> +    machine_class_allow_dynamic_sysbus_dev(mc, "sysbus-debugcon");
> +    machine_class_allow_dynamic_sysbus_dev(mc, "sysbus-debugexit");

Aren't these common to X86?

> +    mc->max_cpus = 288;
> +    mc->has_hotpluggable_cpus = false;
> +    mc->auto_enable_numa_with_memhp = false;
> +    mc->default_cpu_type = TARGET_DEFAULT_CPU_TYPE;
> +    mc->nvdimm_supported = false;
> +
> +    /* Avoid relying too much on kernel components */
> +    mc->default_kernel_irqchip_split = true;
> +
> +    /* Machine class handlers */
> +    mc->reset = microvm_machine_reset;
> +
> +    /* NMI handler */
> +    nc->nmi_monitor_handler = x86_nmi;
> +
> +    object_class_property_add_bool(oc, MICROVM_MACHINE_RTC,
> +                                   microvm_machine_get_rtc,
> +                                   microvm_machine_set_rtc,
> +                                   &error_abort);
> +    object_class_property_set_description(oc, MICROVM_MACHINE_RTC,
> +        "Set off to disable the instantiation of an MC146818 RTC",
> +        &error_abort);
> +
> +    object_class_property_add_bool(oc, MICROVM_MACHINE_ISA_SERIAL,
> +                                   microvm_machine_get_isa_serial,
> +                                   microvm_machine_set_isa_serial,
> +                                   &error_abort);
> +    object_class_property_set_description(oc, MICROVM_MACHINE_ISA_SERIAL,
> +        "Set off to disable the instantiation an ISA serial port",
> +        &error_abort);
> +
> +    object_class_property_add_bool(oc, MICROVM_MACHINE_OPTION_ROMS,
> +                                   microvm_machine_get_option_roms,
> +                                   microvm_machine_set_option_roms,
> +                                   &error_abort);
> +    object_class_property_set_description(oc, MICROVM_MACHINE_OPTION_ROMS,
> +        "Set off to disable loading option ROMs", &error_abort);
> +
> +    object_class_property_add_bool(oc, MICROVM_MACHINE_KERNEL_CMDLINE,
> +                                   microvm_machine_get_kernel_cmdline,
> +                                   microvm_machine_set_kernel_cmdline,
> +                                   &error_abort);
> +    object_class_property_set_description(oc, MICROVM_MACHINE_KERNEL_CMDLINE,
> +        "Set off to disable adding virtio-mmio devices to the kernel 
> cmdline",
> +        &error_abort);
> +}
> +
> +static const TypeInfo microvm_machine_info = {
> +    .name          = TYPE_MICROVM_MACHINE,
> +    .parent        = TYPE_X86_MACHINE,
> +    .instance_size = sizeof(MicrovmMachineState),
> +    .instance_init = microvm_machine_initfn,
> +    .class_size    = sizeof(MicrovmMachineClass),
> +    .class_init    = microvm_class_init,
> +    .interfaces = (InterfaceInfo[]) {
> +         { TYPE_NMI },

Isn't this inherited from TYPE_X86_MACHINE?

> +         { }
> +    },
> +};
> +
> +static void microvm_machine_init(void)
> +{
> +    type_register_static(&microvm_machine_info);
> +}
> +type_init(microvm_machine_init);
> diff --git a/include/hw/i386/microvm.h b/include/hw/i386/microvm.h
> new file mode 100644
> index 0000000000..04c8caf886
> --- /dev/null
> +++ b/include/hw/i386/microvm.h
> @@ -0,0 +1,80 @@
> +/*
> + * Copyright (c) 2018 Intel Corporation
> + * Copyright (c) 2019 Red Hat, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms and conditions of the GNU General Public License,
> + * version 2 or later, as published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along 
> with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef HW_I386_MICROVM_H
> +#define HW_I386_MICROVM_H
> +
> +#include "qemu-common.h"
> +#include "exec/hwaddr.h"
> +#include "qemu/notify.h"
> +
> +#include "hw/boards.h"
> +#include "hw/i386/x86.h"
> +
> +/* Microvm memory layout */
> +#define PVH_START_INFO        0x6000
> +#define MEMMAP_START          0x7000
> +#define MODLIST_START         0x7800
> +#define BOOT_STACK_POINTER    0x8ff0
> +#define PML4_START            0x9000
> +#define PDPTE_START           0xa000
> +#define PDE_START             0xb000
> +#define KERNEL_CMDLINE_START  0x20000
> +#define EBDA_START            0x9fc00
> +#define HIMEM_START           0x100000
> +
> +/* Platform virtio definitions */
> +#define VIRTIO_MMIO_BASE      0xc0000000
> +#define VIRTIO_IRQ_BASE       5
> +#define VIRTIO_NUM_TRANSPORTS 8
> +#define VIRTIO_CMDLINE_MAXLEN 64
> +
> +/* Machine type options */
> +#define MICROVM_MACHINE_RTC            "rtc"
> +#define MICROVM_MACHINE_ISA_SERIAL     "isa-serial"
> +#define MICROVM_MACHINE_OPTION_ROMS    "option-roms"
> +#define MICROVM_MACHINE_KERNEL_CMDLINE "kernel-cmdline"
> +
> +typedef struct {
> +    X86MachineClass parent;
> +    HotplugHandler *(*orig_hotplug_handler)(MachineState *machine,
> +                                           DeviceState *dev);
> +} MicrovmMachineClass;
> +
> +typedef struct {
> +    X86MachineState parent;
> +
> +    /* Machine type options */
> +    bool rtc_enabled;
> +    bool isa_serial_enabled;
> +    bool option_roms_enabled;
> +    bool kernel_cmdline_enabled;
> +
> +
> +    /* Machine state */
> +    bool kernel_cmdline_fixed;
> +} MicrovmMachineState;
> +
> +#define TYPE_MICROVM_MACHINE   MACHINE_TYPE_NAME("microvm")
> +#define MICROVM_MACHINE(obj) \
> +    OBJECT_CHECK(MicrovmMachineState, (obj), TYPE_MICROVM_MACHINE)
> +#define MICROVM_MACHINE_GET_CLASS(obj) \
> +    OBJECT_GET_CLASS(MicrovmMachineClass, obj, TYPE_MICROVM_MACHINE)
> +#define MICROVM_MACHINE_CLASS(class) \
> +    OBJECT_CLASS_CHECK(MicrovmMachineClass, class, TYPE_MICROVM_MACHINE)
> +
> +#endif
>