You say the application runs, right?  So what made you check the SPE
bit state?  The kernel keeps SPE disabled by default so it doesn't
have to save the upper 32 bits of the registers every context
switch.  When a process uses SPE for the first time, an exception is
triggered, the kernel enables SPE for that process, and then that
process should be able to use SPE every time it gets cpu time.

How are you determining that the SPE bit is not set?  Is your
application not executing the SPE instructions?

Andy

Yes the application runs. I wrote a mini driver with an ioctl which
performs a mfmsr() call and  returns the value to the user application.
I called this ioctl at several times before and after executing SPE code.
I already tried to manually force the SPE bit with another ioctl which
performs a enable_kernel_spe() call. The bit SPE is right set at this time
but disappears later.

I don't know if using ioctls is a right way to check the bit.

Any idea ?
Thanks
Gérard