Mark Post wrote:
I'm not aware of any method to tell an IFL apart from a CP, except for trying to execute the one instruction that is different between the two (which IBM no longer talks about in public). I don't think you want to try that route, however, since if you do manage to execute it on an IFL, your system will check stop. Since I'm not familiar with all the new hardware instructions that have been introduced, it's possible that stfle instruction might give you a hint.
Well.. The instruction (SERVC (B220) instruction subcodes 0x00020001 and subcodes 0x00120001) may be "secret" but it is used in the linux kernel which source is legally available for anyone to examine/modify/discuss ! They may not want to talk about it in public, but.. sorry.. the cat is out of the bag ! The layout and invocation can be found in drivers/s390/char/sclp.c and sclp_cmd.c (cf sclp_read_info_early() - which fills in the structure and then invokes sclp_service_call() which invokes the appropriate machine instruction (0xB220)). The thing to remember is : *ALWAYS* invoke function code 0x00120001 first.. and if it fails (that is the response is not 0x10xx) *then* try function code 0x00020001 (and NOT the other way around - lest you want to wind up with a system check stop state if the IPL processor is an IFL - as Mark said). If 0x00120001 succeeds, then it's an IFL.. if 0x00020001 succeeds then it's a CP.. If this fails, you're out of luck (because the IPL processor cannot be anything else than an IFL or CP.. ZIIPs, ZAAPs can't be IPLed and if you have a CF in your config you should only IPL the CF/ICF code). ds) or a CP (0x00120001 fails but 0x00020001 succeeds). This does not account for a possibly mixed CPU config (that is mixed CP and IFLs in the same virtual machine config as I believe z/VM 5.4 allows). AFAIK, the SCLP_READ_INFO IFL/CP quirk only applies to the IPL CPU, not any subsequent CPUs in the virtual configuration. I do not know what is suppose to happen if SERVC 0x00020001/0x00120001 is invoked from a non-IPL processor. Also, this applies to a z/VM virtual machine, a LPAR or.. whatever... Also.. STFLE won't give much hint here.. STFLE only addresses Principles of Operations official 'features', not operational restrictions. --Ivan ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
