Re: [PATCH v4 0/8] Introduce the microvm machine type

[Christian Borntraeger <borntraeger@de.ibm.com>]

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.
> 
> 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)

Just out of curiosity. 
What is the reason for not going virtio-pci? Is the PCI bus really
that expensive and complicated?
FWIW, I do not complain. When people start using virtio-mmio more
often this would also help virtio-ccw (which I am interested in)
as this forces people to think beyond virtio-pci.