On 2011-04-19 11:30, Philippe Gerum wrote:
> On Tue, 2011-04-19 at 11:29 +0200, Philippe Gerum wrote:
>> On Tue, 2011-04-19 at 10:42 +0200, Gilles Chanteperdrix wrote:
>>> Philippe Gerum wrote:
>>>> On Tue, 2011-04-19 at 09:58 +0200, Jesper Christensen wrote:
>>>>> Great thanks, but i can't help wondering if the problems i'm seeing are
>>>>> related to some of my userspace programs using fp.
>>>> I don't think so. The switchtest programs exercises the FPU hardware in
>>>> a certain way to make sure it is available in real-time mode from kernel
>>>> space (which is an utterly crappy legacy, but we will have to deal with
>>>> it until Xenomai 3.x). As far as I can see from your .config, you can't
>>>> have such support, so switchtest was basically trying to test an
>>>> inexistent feature.
>>> In fact, switchtest whether Xenomai FPU switch routines work when the
>>> Linux kernel itself uses FPU in kernel-space. Currently, the only place
>>> when this happens is in the RAID code: x86 uses mmx/sse, and some power
>>> pcs use altivec. Some powerpc also fix unaligned accesses to floating
>>> point data in kernel-space, I do not know if this may interfere, which
>>> is why the powerpc code is compiled even without RAID.
>> AFAICS, fp_regs_set() on ppc is issuing a load float instruction in
>> kernel space which could be unaligned, and therefore trap. Looking at
>> the .config for the target system, hw FPU support is disabled in the
>> alignment code, so basically, this would beget a nop.
> A nop in fixing the issue, I mean.

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