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

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Jun 27, 2018 at 01:31:17PM +0100, Dr. David Alan Gilbert wrote:
> * Hongbo Zhang (hongbo.zhang@linaro.org) 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.

Regards,
Daniel
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