Re: [Qemu-arm] [Qemu-devel] [PATCH v2 2/2] hw/arm: Add Arm Enterprise machine type

[Ard Biesheuvel]

On 25 July 2018 at 11:40, Andrew Jones <address@hidden> wrote:
> On Wed, Jul 25, 2018 at 11:20:03AM +0200, Ard Biesheuvel wrote:
>> On 25 July 2018 at 11:17, Hongbo Zhang <address@hidden> wrote:
>> > On 25 July 2018 at 17:13, Ard Biesheuvel <address@hidden> wrote:
>> >> On 25 July 2018 at 11:09, Hongbo Zhang <address@hidden> wrote:
>> >>> On 25 July 2018 at 17:01, Ard Biesheuvel <address@hidden> wrote:
>> >>>> On 25 July 2018 at 10:48, Daniel P. Berrangé <address@hidden> wrote:
>> >>>>> On Wed, Jul 25, 2018 at 01:30:52PM +0800, Hongbo Zhang wrote:
>> >>>>>> For the Aarch64, there is one machine 'virt', it is primarily meant to
>> >>>>>> run on KVM and execute virtualization workloads, but we need an
>> >>>>>> environment as faithful as possible to physical hardware, for 
>> >>>>>> supporting
>> >>>>>> firmware and OS development for pysical Aarch64 machines.
>> >>>>>>
>> >>>>>> This patch introduces new machine type 'Enterprise' with main 
>> >>>>>> features:
>> >>>>>
>> >>>>> The 'enterprise' name is really awful - this is essentially a marketing
>> >>>>> term completely devoid of any useful meaning.
>> >>>>>
>> >>>>> You had previously called this "sbsa" which IIUC was related to a real
>> >>>>> world hardware specification that it was based on. IOW, I think this 
>> >>>>> old
>> >>>>> name was preferrable to calling it "enterprise".
>> >>>>>
>> >>>>
>> >>>> I couldn't agree more. However, IIUC this change was made at the
>> >>>> request of one of the reviewers, although I wasn't part of the
>> >>>> discussion at that point, so I'm not sure who it was.
>> >>>>
>> >>>> Hongbo, could you please share a link to that discussion?
>> >>>>
>> >>>> Thanks,
>> >>>> Ard.
>> >>>>
>> >>>
>> >>> V1 discussion here:
>> >>> https://www.mail-archive.com/address@hidden/msg545775.html
>> >>>
>> >>
>> >> So who asked for the sbsa -> enterprise change?
>> >
>> > Actually nobody, but it was argued that sbsa does not require ehci and
>> > ahci etc, then we should find a name fitting for this platform better.
>>
>> That doesn't make sense to me. The SBSA describes a minimal
>> configuration, it does not limit what peripherals may be attached to
>> the core system.
>>
>
> Hi Ard,
>
> I think that a machine model named 'sbsa' should provide all SBSA required
> hardware, and nothing else, while providing a means to easily extend the
> machine beyond that in any way the user likes. The user can easily add
> devices with the command line and/or by using -readconfig to build a
> "typical" machine. Note, it should even be possible to add, e.g. an ACHI
> controller, to the memory map using the platform bus, if that's preferred
> over PCIe.
>

The purpose of the SBSA machine is not to provide a minimal
configuration. It is intended to exercise all the moving parts one
might find in a server firmware/OS stack, including pieces that are
not usually found on x86 machines, such as DRAM starting above 4 GB
and SATA/USB controllers that are not PCIe based.

If we start layering the usual components on top, it is highly likely
that checking the EHCI box gives you a PCI based USB2 controller,
partially defeating the purpose of the exercise.

-- 
Ard.