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

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

[Francis Moreau]

Hello,

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. I added a couple of trace to see which one cannot be probed
by the kernel and  I got them:

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:gpio0
amba_device_register failed to register dev:gpio1
amba_device_register failed to register dev:gpio2
amba_device_register failed to register dev:sci0
amba_device_register failed to register dev:ssp0
amba_device_register failed to register fpga:aaci

The "mmci" host driver needs some gpio in order to work.

Is that correct that with qemu 0.14.1, I can't use the SD card interface ?

If so does a latter version of qemu support this ?

If not can somebody point me which files in qemu I should look in
order to do that ?

Thanks.
-- 
Francis

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

[Peter Maydell]

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.

> The "mmci" host driver needs some gpio in order to work.
>
> Is that correct that with qemu 0.14.1, I can't use the SD card interface ?

You need a newer QEMU. The GPIO modules and the wiring for
the MMC card status outputs should be present in QEMU 0.15.
0.14.1 has a number of known ARM bugs (especially in Neon
and VFP emulation) and I do not recommend it for ARM targets.

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.]

-- PMM

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

[Francis Moreau]

Hello Peter,

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 ?"

>> The "mmci" host driver needs some gpio in order to work.
>>
>> Is that correct that with qemu 0.14.1, I can't use the SD card interface ?
>
> You need a newer QEMU. The GPIO modules and the wiring for
> the MMC card status outputs should be present in QEMU 0.15.
> 0.14.1 has a number of known ARM bugs (especially in Neon
> and VFP emulation) and I do not recommend it for ARM targets.

Yes that what I saw when trying the tip of qemu git repo.

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

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

> 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 ?
-- 
Francis

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

[Peter Maydell]

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

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

[Alexander Graf]

On 09.10.2011, at 14:51, Peter Maydell wrote:

> 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.

cache=writeback survives host crashes. The only reason writethrough is the default is Windows XP which doesn't issue flushes properly, so there cache=writeback can lead to data loss. Linux guests are fine.


Alex

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

[Peter Maydell]

On 9 October 2011 16:01, Alexander Graf <agraf@suse.de> wrote:
> cache=writeback survives host crashes. The only reason writethrough
> is the default is Windows XP which doesn't issue flushes properly,
> so there cache=writeback can lead to data loss. Linux guests are fine.

I thought that only applied to disks attached via protocols
(IDE, SCSI) that supported a flush command? SD cards don't,
so no guest issues flushes.

-- PMM

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

[Alexander Graf]

On 09.10.2011, at 17:46, Peter Maydell wrote:

> On 9 October 2011 16:01, Alexander Graf <agraf@suse.de> wrote:
>> cache=writeback survives host crashes. The only reason writethrough
>> is the default is Windows XP which doesn't issue flushes properly,
>> so there cache=writeback can lead to data loss. Linux guests are fine.
> 
> I thought that only applied to disks attached via protocols
> (IDE, SCSI) that supported a flush command? SD cards don't,
> so no guest issues flushes.

Ouch, really? Now that makes SDs even worse than I thought :)


Alex

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

[Francis Moreau]

On Sun, Oct 9, 2011 at 2:51 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
> 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.
>

Ok.

>> 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?

Not really, but it took me some times to realize why booting from SD
interface did work with qemu. So I prefered asking to avoid been hit
by another missing devices later.

> 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.
>

Ok, I'll use this platform from now.

Thanks for your advices.
-- 
Francis

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

[Francis Moreau]

On Sun, Oct 9, 2011 at 6:22 PM, Francis Moreau <francis.moro@gmail.com> wrote:
> On Sun, Oct 9, 2011 at 2:51 PM, Peter Maydell <peter.maydell@linaro.org> wrote:
>> 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.
>>
>
> Ok.
>
>>> 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?
>
> Not really, but it took me some times to realize why booting from SD
> interface did work with qemu. So I prefered asking to avoid been hit

I meant: "why booting from SD interface *didn't* work..."

I noticed another point for the realview platofrm: if I boot with "-M
512", it works however if I set "-M 256" then it doesn't.

Is this expected ?

Thanks
-- 
Francis

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

[Peter Maydell]

On 10 October 2011 08:35, Francis Moreau <francis.moro@gmail.com> wrote:
> I noticed another point for the realview platofrm: if I boot with "-M
> 512", it works however if I set "-M 256" then it doesn't.

Perhaps your kernel is configured to load in the higher 256MB
address range, or is configured/has a command line which assumes
it has 512MB of RAM? (In what way does it "not work" ?)

-- PMM

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

[Francis Moreau]

On Mon, Oct 10, 2011 at 10:42 AM, Peter Maydell
<peter.maydell@linaro.org> wrote:
> On 10 October 2011 08:35, Francis Moreau <francis.moro@gmail.com> wrote:
>> I noticed another point for the realview platofrm: if I boot with "-M
>> 512", it works however if I set "-M 256" then it doesn't.
>
> Perhaps your kernel is configured to load in the higher 256MB
> address range

hmm which options do you have in mind ?

> or is configured/has a command line which assumes
> it has 512MB of RAM? (In what way does it "not work" ?)

I have no such thing in the command line.

When I say "it doesn't work", it means that nothing happen when
starting qemu: no trace, it looks like it's running an infinite loop.

BTW I'm wondering which kernel source I should use to build kernels
for such plateforms (realview, vexpress, versatile) ? I'm currently
using the source from kernel.org (well similar since this server seems
really dead). but I'm not sure if it's a good idea...

Thanks.
-- 
Francis

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

[Peter Maydell]

On 10 October 2011 14:48, Francis Moreau <francis.moro@gmail.com> wrote:
> On Mon, Oct 10, 2011 at 10:42 AM, Peter Maydell
> <peter.maydell@linaro.org> wrote:
>> On 10 October 2011 08:35, Francis Moreau <francis.moro@gmail.com> wrote:
>>> I noticed another point for the realview platofrm: if I boot with "-M
>>> 512", it works however if I set "-M 256" then it doesn't.
>>
>> Perhaps your kernel is configured to load in the higher 256MB
>> address range
>
> hmm which options do you have in mind ?

Hmm, I thought there was an option for this but I can't find it
in the config, so I must have been misremembering somehow.

> When I say "it doesn't work", it means that nothing happen when
> starting qemu: no trace, it looks like it's running an infinite loop.

Not even "Uncompressing the kernel" ?

If you want to track down what's going on then you'll need to
connect an ARM gdb up to qemu and single step through the boot
process, I'm afraid.

> BTW I'm wondering which kernel source I should use to build kernels
> for such plateforms (realview, vexpress, versatile) ? I'm currently
> using the source from kernel.org (well similar since this server seems
> really dead). but I'm not sure if it's a good idea...

I think the mainline kernel sources should in theory work
(in particular if they work with 512MB then that's a good
sign...) but I'm not a kernel expert; mostly I use other peoples'
prebuilt ones.

-- PMM

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

[Francis Moreau]

On Wed, Oct 12, 2011 at 11:23 AM, Peter Maydell
<peter.maydell@linaro.org> wrote:
> On 10 October 2011 14:48, Francis Moreau <francis.moro@gmail.com> wrote:
>> On Mon, Oct 10, 2011 at 10:42 AM, Peter Maydell
>> <peter.maydell@linaro.org> wrote:
>>> On 10 October 2011 08:35, Francis Moreau <francis.moro@gmail.com> wrote:
>>>> I noticed another point for the realview platofrm: if I boot with "-M
>>>> 512", it works however if I set "-M 256" then it doesn't.
>>>
>>> Perhaps your kernel is configured to load in the higher 256MB
>>> address range
>>
>> hmm which options do you have in mind ?
>
> Hmm, I thought there was an option for this but I can't find it
> in the config, so I must have been misremembering somehow.
>
>> When I say "it doesn't work", it means that nothing happen when
>> starting qemu: no trace, it looks like it's running an infinite loop.
>
> Not even "Uncompressing the kernel" ?

yes uncompressing the kernel works. Below is what I'm seeing exactly:

Uncompressing Linux... done, booting the kernel.

>
> If you want to track down what's going on then you'll need to
> connect an ARM gdb up to qemu and single step through the boot
> process, I'm afraid.
>

Ok but that means that I understand the code I'm going to step through :-/

>> BTW I'm wondering which kernel source I should use to build kernels
>> for such plateforms (realview, vexpress, versatile) ? I'm currently
>> using the source from kernel.org (well similar since this server seems
>> really dead). but I'm not sure if it's a good idea...
>
> I think the mainline kernel sources should in theory work
> (in particular if they work with 512MB then that's a good
> sign...) but I'm not a kernel expert; mostly I use other peoples'
> prebuilt ones.

ok, but wouldn't you recommend to use the kernel from Linaro ? ;)

Thanks
-- 
Francis

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

[Peter Maydell]

On 12 October 2011 20:39, Francis Moreau <francis.moro@gmail.com> wrote:
> On Wed, Oct 12, 2011 at 11:23 AM, Peter Maydell
> <peter.maydell@linaro.org> wrote:
>> I think the mainline kernel sources should in theory work
>> (in particular if they work with 512MB then that's a good
>> sign...) but I'm not a kernel expert; mostly I use other peoples'
>> prebuilt ones.
>
> ok, but wouldn't you recommend to use the kernel from Linaro ? ;)

Obviously those work too (and in practice they're the ones
I test most often with). Linaro kernels will certainly have
been tested with Versatile Express, but probably not with the
other older ARM devboards. But if you don't need to be on the
bleeding edge for anything then I don't think it makes much
difference whether you use the Linaro kernel or mainline for
an established platform like the ARM devboards.
(more info on the aims of the linaro kernel tree here:
https://wiki.linaro.org/WorkingGroups/Kernel/KernelTree
)

-- PMM

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

[Francis Moreau]

On Wed, Oct 12, 2011 at 10:46 PM, Peter Maydell
<peter.maydell@linaro.org> wrote:
> On 12 October 2011 20:39, Francis Moreau <francis.moro@gmail.com> wrote:
>> On Wed, Oct 12, 2011 at 11:23 AM, Peter Maydell
>> <peter.maydell@linaro.org> wrote:
>>> I think the mainline kernel sources should in theory work
>>> (in particular if they work with 512MB then that's a good
>>> sign...) but I'm not a kernel expert; mostly I use other peoples'
>>> prebuilt ones.
>>
>> ok, but wouldn't you recommend to use the kernel from Linaro ? ;)
>
> Obviously those work too (and in practice they're the ones
> I test most often with). Linaro kernels will certainly have
> been tested with Versatile Express, but probably not with the
> other older ARM devboards. But if you don't need to be on the
> bleeding edge for anything then I don't think it makes much
> difference whether you use the Linaro kernel or mainline for
> an established platform like the ARM devboards.
> (more info on the aims of the linaro kernel tree here:
> https://wiki.linaro.org/WorkingGroups/Kernel/KernelTree
> )


Thanks a lot for your answers.

-- 
Francis