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Re: Upgrading the minimum required s390x CPU to z10?

On 2016-05-31 18:18, Stephen Powell wrote:
> On Tue, May 31, 2016, at 17:41, Aurelien Jarno wrote:
> > Hi all,
> > 
> > The Debian s390x port currently defaults to the z900 instruction set. It 
> > appears that an increasing but small number of packages use z10 assembly 
> > code, and need to be patched to be built on Debian. I therefore wonder if
> > it is time to switch the default ISA to z10 (which is the maximum we can 
> > do with out current build daemons and porterbox). Of course that will be
> > done in testing/unstable, so people using older machines can still use
> > jessie.
> > 
> > Any opinion on that?
> > 
> That would count me out.  The latest release of Hercules appears to support
> the z10 instructions, but my employer's real mainframe, on which we run
> Debian images (both jessie and stretch) is a z890.  An instruction not supported
> by a z890 would instantly crash the server.

Ok, good to know we still have users on such hardware.

> Even zIPL has been rewritten in C now.  Why are these new packages using
> assembly language?  And if they are wanting to use an instruction which is
> not supported on all z/Architecture processors, why don't they do a facility
> check first, like they are supposed to, to check to see if the facility required
> to support the instruction is installed?  That's the "right" way to do it.
> And that's what the kernel does.

That's indeed the right way to do it (and to fix the issue), but the
point is that developers using GCC defaulting to z10 or higher don't
realize they can't use the corresponding instructions, so that has to
be fixed later. Latest example is openssl.


Aurelien Jarno                          GPG: 4096R/1DDD8C9B
aurelien@aurel32.net                 http://www.aurel32.net

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