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

[David Hildenbrand <david@redhat.com>]

On 25.09.19 10:10, Sergio Lopez wrote:
> 
> David Hildenbrand <david@redhat.com> 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.
>>>
>>> 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)
>>
>> So I assume also no ACPI (CPU/memory hotplug), correct?
> 
> Correct.
> 
>> @Pankaj, I think it would make sense to make virtio-pmem play with
>> virtio-mmio/microvm.
> 
> That would be great. I'm also looking forward for virtio-mem (and an
> hypothetical virtio-cpu) to eventually gain hotplug capabilities in
> microvm.

@Pankaj, do you have time to look into the virtio-pmem thingy? I guess
the virtio-mmio rapper shouldn't be too hard (very similar to the
virtio-pci wrapper - luckily I insisted to make it work independently
from PCI BARs and ACPI slots ;) ). The microvm bits would be properly
setting up device memory and wiring up the hotplug handlers, similar as
done in the other PC machine types (maybe that comes for free?).

virtio-pmem will allow (in read-only mode) to place the rootfs on a fake
NVDIMM, as done e.g., in kata containers. We might have to include the
virtio-pmem kernel module in the initramfs, shouldn't  be too hard. Not
sure what else we'll need to make virtio-pmem get used as a rootfs.

> 
> Thanks,
> Sergio.
> 


-- 

Thanks,

David / dhildenb