Re: [PATCH v4 7/8] docs/microvm.txt: document the new microvm machine type

[Sergio Lopez]

Paolo Bonzini <address@hidden> writes:

> On 24/09/19 14:44, Sergio Lopez wrote:
>> +Microvm is a machine type inspired by both NEMU and Firecracker, and
>> +constructed after the machine model implemented by the latter.
>
> I would say it's inspired by Firecracker only.  The NEMU virt machine
> had virtio-pci and ACPI.

Actually, the NEMU reference comes from the fact that, originally,
microvm.c code was based on virt.c, but on v4 all that is already gone,
so it makes sense to remove the reference.

>> +It's main purpose is providing users a minimalist machine type free
>> +from the burden of legacy compatibility,
>
> I think this is too strong, especially if you keep the PIC and PIT. :)
> Maybe just "It's a minimalist machine type without PCI support designed
> for short-lived guests".

OK.

>> +serving as a stepping stone
>> +for future projects aiming at improving boot times, reducing the
>> +attack surface and slimming down QEMU's footprint.
>
> "Microvm also establishes a baseline for benchmarking QEMU and operating
> systems, since it is optimized for both boot time and footprint".

Well, I prefer my paragraph, but I'm good with either.

>> +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
>
> Do we need the PIT?  And perhaps the PIC even?

We need the PIT for non-KVM accel (if present with KVM and
kernel_irqchip_split = off, it basically becomes a placeholder), and the
PIC for both the PIT and the ISA serial port.

Thanks,
Sergio.

>> + - MC146818 RTC (optional)
>> + - kvmclock (if using KVM)
>> + - fw_cfg
>> + - One ISA serial port (optional)
>> + - Up to eight virtio-mmio devices (configured by the user)
>> +

signature.asc
Description: PGP signature