Re: [Qemu-devel] [PATCH 0/4] Introduce the microvm machine type

[Sergio Lopez <slp@redhat.com>]

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Paolo Bonzini <pbonzini@redhat.com> writes:

> On 28/06/19 13:53, Sergio Lopez wrote:
>> qemu-system-x86_64 -M microvm,legacy -m 512m -smp 2 \
>>  -kernel vmlinux -append "console=ttyS0 root=/dev/vda" \
>>  -nodefaults -no-user-config \
>>  -drive id=test,file=test.img,format=raw,if=none \
>>  -device virtio-blk-device,drive=test \
>>  -netdev tap,id=tap0,script=no,downscript=no \
>>  -device virtio-net-device,netdev=tap0 \
>>  -serial stdio
>
> I think the "non-legacy" mode can be obtained from the "legacy" one just
> with -nodefaults (which all sane management should be using anyway), so
> legacy=on can actually be the default. :)

I'm a bit confused here. The "legacy" boolean property in the microvm
machine type is used to indicate that QEMU should instantiate an i8259
PIC and an ISA bus (mainly to have easy access to "isa-serial"), instead
of relying on KVM's LAPIC+IOAPIC exclusively.

> I think this is interesting.  I'd love to have it optionally provide a
> device tree as well.  It's not very common on x86 and most distro
> kernels don't support device tree, but it would provide a more
> out-of-the-box experience and it may even be a drop-in replacement for
> q35 or pc as far as Kata is concerned.

I guess generating a dtb and having the kernel parse it will eat some
valuable microseconds but, as you say, it may be a good idea adding it
in the future, as long it's optional.

Sergio.

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