FP context switching on i386

Thomas Doerfler Thomas.Doerfler at embedded-brains.de
Sat Oct 3 22:19:06 UTC 2009

Eric Valette schrieb:
> Thomas Doerfler wrote:
>> How is the FPU controlled in i386?
> Do not remember exactly. Have no data book handy here. Its clear that if
> it is and MSR bit, extra care shall be taken when restoring next
> runnable thread MSR.
That's not the only issue. since interrupt disable/enable also works
with MSR, a thread may have copys of the MSR that are not visible to the
thread dispatcher. So it is very important that the application modifes
the MSR only with proper macros, that do not change the FP bit.


> -- eric
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