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

From: Hongbo Zhang <hongbo.zhang@linaro.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: "Andrew Jones" <drjones@redhat.com>,
	"Radoslaw Biernacki" <radoslaw.biernacki@linaro.org>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"QEMU Developers" <qemu-devel@nongnu.org>,
	"Leif Lindholm" <leif.lindholm@linaro.org>,
	qemu-arm <qemu-arm@nongnu.org>,
	"Alex Bennée" <alex.bennee@linaro.org>
Subject: Re: [Qemu-devel] [PATCH v2 2/2] hw/arm: Add Arm Enterprise machine type
Date: Thu, 26 Jul 2018 18:27:44 +0800	[thread overview]
Message-ID: <CAHmQWvDZytNXkw05DAnq_5HY3RN_UZUpue4kQ2-xSb+75SPgAg@mail.gmail.com> (raw)
In-Reply-To: <CAFEAcA8wi2QV9cVg_Hp=8MYw_zfxvVciR2CbRZiGJNiQNPdHqg@mail.gmail.com>

On 25 July 2018 at 20:19, Peter Maydell <peter.maydell@linaro.org> wrote:
> On 25 July 2018 at 12:44, Andrew Jones <drjones@redhat.com> wrote:
>> On Wed, Jul 25, 2018 at 06:46:59PM +0800, Hongbo Zhang wrote:
>>> For Armv7, there is one typical platform 'vexpress', but for Armv8, no
>>
>> Wasn't the vexpress model designed for a specific machine?
>
> Yes.
>
>> Namely for
>> Arm's simulator?
>
> No.
>
>> Is the vexpress model really something typical among
>> all the Armv7 platforms?
>
> No.
>
> "Vexpress" is a model specifically of a development board
> produced by Arm (the versatile express). It's useful if you
> want to run code that runs on that devboard, but (as with
> most of the devboards we model), it's not necessarily ideal,
> because it has all the limitations of the real hardware it's
> modelling (in this case the big ones are limited memory, no PCI).
> The hardware it models is also quite old now (maybe 7 or 8 years)
> and it's not really "typical" of anything. (In the primarily
> embedded space where most v7 CPUs are there's not really anything
> that could be described as "typical" anyway: everything is
> different.)
>
> For most people who just want to run Linux on an emulated v7 CPU,
> I would recommend the "virt" board, for the same reasons I
> recommend it for v8 cores.
>
>>> such typical one, the 'virt' is typically for running workloads, one
>>> example is using it under OpenStack.
>>> So a 'typical' one for Armv8 is needed for firmware and OS
>>> development, similar like 'vexpress' for Armv7.
>>
>> What is a "typical" Armv8 machine? What will a typical Armv8 machine be in
>> two years?
>>
>> Note, I'm not actually opposed to the current definition (because I don't
>> really have one myself). I'm just opposed to hard coding one.
>
> AIUI the aim here is to provide an emulated platform that is
> set up in the way that server-style armv8 machines are
> recommended to be set up, so it can be used as a testbed and
> demonstration for the firmware/OS software stack. The hope
> is that following "best practices" results in a "typical"
> machine :-)  But the word "typical" is probably not really
> very helpful here...
Yes the aim is truely like that.
Let's forget the word 'typical', a none-english speaker may has his
slightly different understanding according to his own language
culture...

>
> I would expect that in the future we'd want this machine type
> to evolve with the recommendations for how to build server
> platform hardware, which might indeed be different in two years,
> since it would be the development platform for writing/testing
> the firmware/OS stack for that two-years-time hardware.
>
> thanks
> -- PMM