Messages in this thread | | | Date | Sat, 12 Dec 2015 02:43:48 -0600 | From | Segher Boessenkool <> | Subject | Re: Crypto/nx842: Ignore invalid XER[S0] return error |
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On Fri, Dec 11, 2015 at 07:30:29PM -0800, Haren Myneni wrote: > NX842 coprocessor sets 3rd bit in CR register with XER[S0] which is > nothing to do with NX request. On powerpc, XER[S0] will be set if > overflow in FPU and stays until another floating point operation is > executed. Since this bit can be set with other valuable return status, > ignore this XER[S0] value.
XER[SO] is the *integer* summary overflow bit. It is set by OE=1 instructions ("addo" and the like), and can only be cleared explicitly (using "mtxer").
The floating point overflow bit is FPSCR[OX].
> + /* > + * NX842 coprocessor sets 3rd bit in CR register with XER[S0]. > + * Setting XER[S0] happens if overflow in FPU and stays until > + * other floating operation is executed. XER[S0] value is nothing > + * to NX and no use to user. Since this bit can be set with other > + * return values, ignore this error. > + */ > + if (ret & ICSWX_XERS0) > + ret &= ~ICSWX_XERS0;
You can just always clear it, there is no need to check if it is set first.
Segher
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