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

[Sergio Lopez <slp@redhat.com>]

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Stefano Garzarella <sgarzare@redhat.com> writes:

> 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 <slp@redhat.com>
>> ---
>>  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.

I agree, thanks for the suggestion. I'll add support for it.

Sergio.

> 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


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