On 20.09.2017 15:23, Richard Henderson wrote: > On 09/19/2017 02:36 PM, David Hildenbrand wrote: >> On 19.09.2017 19:47, Richard Henderson wrote: >>> On 09/19/2017 09:26 AM, David Hildenbrand wrote: >>>> + const uint8_t fc = env->regs[0] & 0x7fULL; >>> >>> Don't mask here... >> >> Bit 56 is the mod bit (see variable "mod") and is checked inside the >> switch(). The function code really is just composed of bit 57 - 63, so >> this is correct. > > "mod bit"? > > # Bit 56 of general register 0 must be zero; oth- > # erwise, a specification exception is recognized. > > I don't suppose this is a change in PoO v11? I'm still looking at v10. >
I'm also looking at v10. This bit is called "M" bit for all cpacf instructions that allow en/decryption. M == modifier bit == mod bit == bit 56 e.g. for KM (7-56) "When the modifier bit in general register 0 is one, a decipher operation is performed. ...". For instructions that don't allow switching between de/encryption (e.g. KLMD), the modifier bit a.k.a. bit 56 must not be set. I don't really see the need here to rename mod -> bit_56 here. Thank! -- Thanks, David
