On Thursday, 05/04/2006 at 02:19 EST, James Melin <[EMAIL PROTECTED]> wrote: > I just want to reconcile what the People here are saying with what the folk on > the list say regarding what constitutes a 3rd level guest.... > > I'm being told by our head sysprog AND someone else with considerably more VM > experience (he's the new guy) that in Basic mode, the DR VM system is > first Level, our VM is second level and therefore any guests running under OUR > VM are second level. > > It sounds to me like people here on the are saying that the DR VM system is > first level, OUR VM system is second level, and the Linux Guests running > under our VM under the DR vendor VM are in fact executing third level, and > hitting the SIE not in hardware problem. > > Which is correct?
LOL. It just depends on training and local custom. Some people use the "level" to describe levels of virtualization. There is "1st-level SIE" (SIE1) and "2nd-level SIE" (SIE2), so some say that any operating system which runs under the ausipices of SIE2 is a "2nd-level guest". But I would say the majority would use "3rd level" to describe the guests of a 2nd level z/VM system. In Basic mode, 1st level CP (CP1) uses SIE1 to dispatch the the 2nd level CP (CP2), which uses SIE2 to run your 3rd-level guest (Guest3). Everything is wonderful. In LPAR mode, LPAR uses SIE1 to dispatch CP1, which uses SIE2 to dispatch CP2, leaving leaves none for Guest3. This means that when CP2 issues the SIE instruction, it will cause a SIE2 break on CP1. That, in turn, causes CP1 to construct a SIE descriptor, converting CP2's view of Guest3 to that viewed by CP1, or to simulate whatever needs to be simulated. This process is called "Virtual SIE" (VSIE). The itty bitty time slices and possibly small amount of resident guest memory in CP1 real memory means that VSIE doesn't perform very well. Are we having fun yet? Alan Altmark z/VM Development IBM Endicott ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
