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

[Sergio Lopez <slp@redhat.com>]

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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 25/09/19 07:49, Sergio Lopez wrote:
>>>> +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.
>
> You're right my version sort of missed the point.  What about
> s/benchmarking/benchmarking and optimizing/?
>
>>>> +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)
>
> Why?

Perhaps I'm missing something. Is some other device supposed to be
acting as a HW timer while running with TCG acceleration?

>> and the
>> PIC for both the PIT and the ISA serial port.
>
> Can't the ISA serial port work with the IOAPIC?

Hm... I'm not sure. I wanted to give it a try, but then noticed that
multiple places in the code (like hw/intc/apic.c:560) do expect to have
an ISA PIC present through the isa_pic global variable.

I guess we should be able to work around this, but I'm not sure if it's
really worth it. What do you think?

Thanks,
Sergio.

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