Re: [Qemu-devel] [PATCH] hw/arm: Add SBSA machine type

[Hongbo Zhang]

On 28 June 2018 at 18:22, Daniel P. Berrangé <address@hidden> wrote:
> On Wed, Jun 27, 2018 at 01:31:17PM +0100, Dr. David Alan Gilbert wrote:
>> * Hongbo Zhang (address@hidden) wrote:
>> > This patch introduces a new Arm machine type 'SBSA' with features:
>> >  - Based on legacy 'virt' machine type.
>
> The 'virt' machine type is absolutely *not* legacy. It is the preferred
> modern, legacy-free machine type when running virtual machines. Since
> aarch64 is greenfield, there is no compelling reason to emulate a
> specific physical machine for VMs, hence the 'virt' machine type.
>
>> >  - Newly designed memory map.
>> >  - EL2 and EL3 are enabled by default.
>> >  - AHCI controller attached to system bus, and then CDROM and hard disc
>> >    can be added to it.
>> >  - EHCI controller attached to system bus, with USB mouse and key board
>> >    installed by default.
>> >  - E1000 ethernet card on PCIE bus.
>
>> >  - VGA display adaptor on PCIE bus.
>> >  - Default CPU type cortex-a57, 4 cores, and 1G bytes memory.
>> >  - No virtio functions enabled, since this is to emulate real hardware.
>>
>> I'm a bit confused; do you have real modern ARM hardware that has an
>> e1000 on it?  If I understand correctly, e1000 is the old PCI version
>> and the e1000e is at least the more modern PCIe version which makes
>> more sense if you're building on PCIe.
>
> Indeed, it makes little sense to default to e1000 if the goal is to make
> it legacy-free
>
>> However, if you:
>>   a) Don't have real hardware with the e1000 on
>>   b) Do have PCIe
>>
>> then to my mind it makes sense to use virtio-net-pci rather than
>> an e1000e.
>
> If it does down the virtio-* route though, I fail to see any point in
> adding the new machine type at all -  'virt' machine type is intended
> to be used for guests where everything is paravirtualized, ignoring
> physical hardware constraints.
>
Your comment comes earlier than I replied to Laszlo Ersek:

I said "yes yes yes" to him due to he describes the purpose so well,
even better than me.

And the I had some misunderstanding of term 'legacy' too, as I
explained in that reply.

> Regards,
> Daniel
> --
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