Re: [Qemu-devel] [Bug 929638] Re: qemu 1.0 unable to compile on the pandaboard ES

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

On 9 February 2012 19:12, Alexander Graf <agraf@suse.de> wrote:
>
> On 09.02.2012, at 20:11, Peter Maydell wrote:
>
>> On 9 February 2012 18:23, Andreas Färber <afaerber@suse.de> wrote:
>>> Am 09.02.2012 18:07, schrieb Peter Maydell:
>>>> (2) qemu 1.0 does not work on ARM hosts -- see the release notes.
>>>> (3) at least one of the problems which meant we marked it as unsupported is still unfixed in master, so this isn't going to work
>>>
>>> What's the remaining issue? I was able to successfully compile and run
>>> arm-softmmu + arm-linux-user on Oneiric the weekend.
>>
>> On ARM Linux glibc provides a makecontext() that always fails ENOSYS,
>> so our configure test thinks there is makecontext support but when we
>> try to use it for coroutines it will fail and we abort.
>>
>> I have a workaround in qemu-linaro that just forces the makecontext
>> test to fail on ARM but I don't like that much. It would be better
>> to either drop our requirement for makecontext (Paolo had some patches
>> to try to do this IIRC) or to handle it failing at runtime.
>
> Or make the configure test be an execution test and always disable it for cross-compile?

Don't like that idea much either :-)

Really what I want is for ARM hosts to be using the same execution
paths as x86, because being on a less-tested fallback code path
is likely to result in hitting more bugs. So either we should
make qemu not rely on makecontext or we should get makecontext
added to glibc (David Gilbert has an implementation which we're
attempting to submit to eglibc) and make sure that configure/qemu
can cope with both ARM systems with working makecontext and the
old ones without.

-- PMM