Re: calling giveup_altivec on machine with no altivec!?

Troy Benjegerdes wrote:

My Motorola MTX just crashed after the following code in _swithc_to
executed:

        if ((prev->thread.regs && (prev->thread.regs->msr & MSR_VEC)))
                giveup_altivec(prev);

Somehow prev->thread.regs->msr & MSR_VEC turned out true. I'm suspecting
something got overwritten somewhere..

This is an SMP machine so I'm wondering if there wasn't a race condition
on something with task structs..

Is it possible that the MSR had the MSR_VEC bit set at some point?  One
IBM processor user's manual says "the reserved fields should be written
as 0 and read as __undefined__.  This is, when writing to a register with
a reserved field, write a 0 to the reserved field.  When reading from a
register with a reserved field, ignore that bit."

-Frank
--
Frank Rowand [off-list ref]
MontaVista Software, Inc

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