On Tue, 16 Oct 2001, David Edelsohn wrote:

> >>>>> One Without Reason writes:
> 
> Sridhar> Sort of.  It supports the S/390 G4 and higher.  Doesn't support the S/390
> Sridhar> G1, the ES/9000, or others.  Basically what I am doing is to move all the
> Sridhar> code for the S/390-Ri4+ instruction set onto its own compiler flag.  
> Sridhar> Finding exactly where all these instructions are is taking time.  It'll
> Sridhar> take me another month or so.  When I am done, though, I will be able to
> Sridhar> get the NetBSD kernel working on any IBM mainframe newer than the ES/9000
> Sridhar> 9021, and maybe even older systems than that.
> 
> 	I assume that you are aware of the S/390 "Principles of Operation"
> documentation available on IBM websites as HTML, PDF, and BookMgr format:
> 
> http://publibz.boulder.ibm.com/

Indeed I do.  This would royally suck without the help of that document.

> 	Documentation for all generations of the S/390 architecture are
> online for comparison, including details of changes in the introduction of
> each revision.
> 
> 	I believe that one of the dependencies on G4 and above for Linux
> kernel support was the addition of a privileged instruction for SMP
> support.  For a UP kernel, NetBSD (and Linux) could run on an earlier
> generation system.

That's the problem.  There are a couple of others, as well.  Some user
software apparently makes use of instructions not present on the earlier
generation systems too.  I'd rather just make it possible for a single
kernel to be able to boot any of these machines.  Far in the future, even
64-bit support for the zSeries.

> 	It would be wonderful to modularize the GCC support to allow
> runtime choice of S/390 generation, and even S/370 support.  Merging the
> GCC "i370" port into the s390 port would be great.  That work was not
> within the mandate of the IBMers who developed the port.

Actually, I am basing my work on the Linux-S/390-Vintage work.  They did
quite a bit of preliminary stuff looking into recompilation before they
settled on emulation of the missing stuff.  It would indeed be neat to get
GCC onto the S/370.  I might take a crack at it after I get the
older-generation S/390 stuff in.  Unless, that is, you want to do it. 8-)

Peace...  Sridhar