Re: [Qemu-devel] Is realview-pb-a8 fully supported ?

[Peter Maydell <peter.maydell@linaro.org>]

On 9 October 2011 13:06, Francis Moreau <francis.moro@gmail.com> wrote:
> On Sun, Oct 9, 2011 at 12:48 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
>> On 9 October 2011 09:28, Francis Moreau <francis.moro@gmail.com> wrote:
>>> I'm trying to use qemu to emulate the ARM realview-pb-a8 and more
>>> specifically I'd like to boot using the SD interface.
>>>
>>> However it looks like some devices are not emulated at all on this
>>> platform.
>>
>> Correct; not all devices are emulated.

> May I suggest to report that a platform is partially supported when
> doing "qemu -M ?"

I suspect that (in the sense you seem to be using "partially supported")
would cover almost all the platforms QEMU supports. Device and board
modelling is not trivial, and the typical state is that devices may be
missing, or have unimplemented features, or have bugs.

The platform is supported in the sense that if you report regressions
(ie things that used to work and have broken) I will look at them, and
if you submit patches to improve it I will review them.

> However, those are still missing:
>
> amba_device_register failed to register dev:smc
> amba_device_register failed to register dev:sctl
> amba_device_register failed to register dev:wdog
> amba_device_register failed to register dev:sci0
> amba_device_register failed to register dev:ssp0
> amba_device_register failed to register fpga:aaci

Do you actually *need* these devices? If so, you're
going to need to model them. (except "fpga:aaci", which
is the PL041 audio; there are patches going through review
for that currently.) But in general Linux will quite happily
boot even if some of the minor devices are missing.

> In your opinion, which plateform should I use to get a fully supported
> platform based on ARMv7 cpu ?

I would recommend vexpress-a9 over realview-pb-a8 simply because
it's newer; nobody cares much about pb-a8 hardware any more.
The actual level of support (in terms of which devices are
present and how fully featured they are) is about the same, though.

>> NB: when booting off SD card make sure you use
>> "-drive if=sd,cache=writeback,file=your-sd.img", otherwise you
>> will get the writethrough cache and really poor I/O performance.
>> [the slight catch is that if your *host* system crashes you
>> may get disk corruption, but typically for ARM emulation use
>> cases that is acceptable.]
>
> Thanks for the tip but why not making writeback the defaut ?

Because of the 'slight catch' I mentioned.

-- PMM