Re: [Qemu-devel] [PATCH v2 4/4] hw/i386: Introduce the microvm machine type

[Stefano Garzarella]

On Mon, Jul 01, 2019 at 04:47:05PM +0200, 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 KVM-only machine type with fast
> boot times, minimal attack surface (measured as the number of IO ports
> and MMIO regions exposed to the Guest) and small footprint (specially
> when combined with the ongoing QEMU modularization effort).
> 
> Normally, other than the device support provided by KVM itself,
> microvm only supports virtio-mmio devices. Microvm also includes a
> legacy mode, which adds an ISA bus with a 16550A serial port, useful
> for being able to see the early boot kernel messages.
> 
> Microvm only supports booting PVH-enabled Linux ELF images. Booting
> other PVH-enabled kernels may be possible, but due to the lack of ACPI
> and firmware, we're relying on the command line for specifying the
> location of the virtio-mmio transports. If there's an interest on
> using this machine type with other kernels, we'll try to find some
> kind of middle ground solution.
> 
> 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                | 500 +++++++++++++++++++++++++++++++
>  include/hw/i386/microvm.h        |  77 +++++
>  5 files changed, 583 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..338f07420f 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
> diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
> index 9817888216..94c565d8db 100644
> --- a/hw/i386/Kconfig
> +++ b/hw/i386/Kconfig
> @@ -87,6 +87,10 @@ config Q35
>      select VMMOUSE
>      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 c5f20bbd72..7bffca413e 100644
> --- a/hw/i386/Makefile.objs
> +++ b/hw/i386/Makefile.objs
> @@ -4,6 +4,7 @@ obj-y += pvh.o
>  obj-y += pc.o
>  obj-$(CONFIG_I440FX) += pc_piix.o
>  obj-$(CONFIG_Q35) += pc_q35.o
> +obj-$(CONFIG_MICROVM) += mptable.o microvm.o
>  obj-y += fw_cfg.o pc_sysfw.o
>  obj-y += x86-iommu.o
>  obj-$(CONFIG_VTD) += intel_iommu.o
> diff --git a/hw/i386/microvm.c b/hw/i386/microvm.c
> new file mode 100644
> index 0000000000..8b5efe9e45
> --- /dev/null
> +++ b/hw/i386/microvm.c
> @@ -0,0 +1,500 @@
> +/*
> + * 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 "qapi/error.h"
> +#include "qapi/visitor.h"
> +#include "sysemu/sysemu.h"
> +#include "sysemu/cpus.h"
> +#include "sysemu/numa.h"
> +
> +#include "hw/loader.h"
> +#include "hw/nmi.h"
> +#include "hw/kvm/clock.h"
> +#include "hw/i386/microvm.h"
> +#include "hw/i386/pc.h"
> +#include "target/i386/cpu.h"
> +#include "hw/timer/i8254.h"
> +#include "hw/char/serial.h"
> +#include "hw/i386/topology.h"
> +#include "hw/virtio/virtio-mmio.h"
> +#include "hw/i386/mptable.h"
> +
> +#include "cpu.h"
> +#include "elf.h"
> +#include "pvh.h"
> +#include "kvm_i386.h"
> +#include "hw/xen/start_info.h"
> +
> +static void microvm_gsi_handler(void *opaque, int n, int level)
> +{
> +    qemu_irq *ioapic_irq = opaque;
> +
> +    qemu_set_irq(ioapic_irq[n], level);
> +}
> +
> +static void microvm_legacy_init(MicrovmMachineState *mms)
> +{
> +    ISABus *isa_bus;
> +    GSIState *gsi_state;
> +    qemu_irq *i8259;
> +    int i;
> +
> +    assert(kvm_irqchip_in_kernel());
> +    gsi_state = g_malloc0(sizeof(*gsi_state));
> +    mms->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, mms->gsi);
> +
> +    assert(kvm_pic_in_kernel());
> +    i8259 = kvm_i8259_init(isa_bus);
> +
> +    for (i = 0; i < ISA_NUM_IRQS; i++) {
> +        gsi_state->i8259_irq[i] = i8259[i];
> +    }
> +
> +    kvm_pit_init(isa_bus, 0x40);
> +
> +    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,
> +                             mms->gsi[VIRTIO_IRQ_BASE + i]);
> +    }
> +
> +    g_free(i8259);
> +
> +    serial_hds_isa_init(isa_bus, 0, 1);
> +}
> +
> +static void microvm_ioapic_init(MicrovmMachineState *mms)
> +{
> +    qemu_irq *ioapic_irq;
> +    DeviceState *ioapic_dev;
> +    SysBusDevice *d;
> +    int i;
> +
> +    assert(kvm_irqchip_in_kernel());
> +    ioapic_irq = g_new0(qemu_irq, IOAPIC_NUM_PINS);
> +    kvm_pc_setup_irq_routing(true);
> +
> +    assert(kvm_ioapic_in_kernel());
> +    ioapic_dev = qdev_create(NULL, "kvm-ioapic");
> +
> +    object_property_add_child(qdev_get_machine(),
> +                              "ioapic", OBJECT(ioapic_dev), NULL);
> +
> +    qdev_init_nofail(ioapic_dev);
> +    d = SYS_BUS_DEVICE(ioapic_dev);
> +    sysbus_mmio_map(d, 0, IO_APIC_DEFAULT_ADDRESS);
> +
> +    for (i = 0; i < IOAPIC_NUM_PINS; i++) {
> +        ioapic_irq[i] = qdev_get_gpio_in(ioapic_dev, i);
> +    }
> +
> +    mms->gsi = qemu_allocate_irqs(microvm_gsi_handler,
> +                                  ioapic_irq, IOAPIC_NUM_PINS);
> +
> +    for (i = 0; i < VIRTIO_NUM_TRANSPORTS; i++) {
> +        sysbus_create_simple("virtio-mmio",
> +                             VIRTIO_MMIO_BASE + i * 512,
> +                             mms->gsi[VIRTIO_IRQ_BASE + i]);
> +    }
> +}
> +
> +static void microvm_memory_init(MicrovmMachineState *mms)
> +{
> +    MachineState *machine = MACHINE(mms);
> +    MemoryRegion *ram, *ram_below_4g, *ram_above_4g;
> +    MemoryRegion *system_memory = get_system_memory();
> +
> +    if (machine->ram_size > MICROVM_MAX_BELOW_4G) {
> +        mms->above_4g_mem_size = machine->ram_size - MICROVM_MAX_BELOW_4G;
> +        mms->below_4g_mem_size = MICROVM_MAX_BELOW_4G;
> +    } else {
> +        mms->above_4g_mem_size = 0;
> +        mms->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, mms->below_4g_mem_size);
> +    memory_region_add_subregion(system_memory, 0, ram_below_4g);
> +
> +    e820_add_entry(0, mms->below_4g_mem_size, E820_RAM);
> +
> +    if (mms->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,
> +                                 mms->below_4g_mem_size,
> +                                 mms->above_4g_mem_size);
> +        memory_region_add_subregion(system_memory, 0x100000000ULL,
> +                                    ram_above_4g);
> +        e820_add_entry(0x100000000ULL, mms->above_4g_mem_size, E820_RAM);
> +    }
> +}
> +
> +static void microvm_cpus_init(const char *typename, Error **errp)
> +{
> +    int i;
> +
> +    for (i = 0; i < smp_cpus; i++) {
> +        Object *cpu = NULL;
> +        Error *local_err = NULL;
> +
> +        cpu = object_new(typename);
> +
> +        object_property_set_uint(cpu, i, "apic-id", &local_err);
> +        object_property_set_bool(cpu, true, "realized", &local_err);
> +
> +        object_unref(cpu);
> +        error_propagate(errp, local_err);
> +    }
> +}
> +
> +static void microvm_machine_state_init(MachineState *machine)
> +{
> +    MicrovmMachineState *mms = MICROVM_MACHINE(machine);
> +    Error *local_err = NULL;
> +
> +    if (machine->kernel_filename == NULL) {
> +        error_report("missing kernel image file name, required by microvm");
> +        exit(1);
> +    }

Could it be useful to support initrd as well?

I'm thinking a possibility to a microvm to use only the initrd without a
block device.

In this case, Linux expects the initrd address and size in the first
element of the modlist in the 'struct hvm_start_info'.

See pc-bios/optionrom/pvh_main.c

Cheers,
Stefano