Most program checks are handled by sie, with the exception of protection, addressing, specification and special operation exception. VM will also request interception for an operation exception in order to catch the iucv instruction. Now this is as described in the sie manual, I think that the protection exception has changed since the manual was written, and I suspect that it only causes an interception on a host protection exception. The specification exception causes overhead when running linux on a machine with no ieee float, as quite a few of the existing float instructions (such as LD) will cause a specification exception when non existent registers are addressed, and as such will cuase a sie intercept, when the linux guest is redispatched, it will perform the program check, and emulate the fp instruction, hence the overhead.
Jan Jaeger Rob van der Heij wrote: > > If nothing else the CPTRACE table will show you what intercepts > you get. V=F applies only when you run VM in basic mode. > I think some of the program checks are handled by SIE, and some > are not. This was why we argued long ago about prefixing BFP > instructions with an SVC rather than let it program check on them. > > Rob
