Re: [PATCH v3 02/13] tcg/s390x: Remove TCG_REG_TB

[Ilya Leoshkevich <iii@linux.ibm.com>]

On Wed, 2022-12-07 at 08:55 -0600, Richard Henderson wrote:
> On 12/7/22 01:45, Thomas Huth wrote:
> > On 06/12/2022 23.22, Richard Henderson wrote:
> > > On 12/6/22 13:29, Ilya Leoshkevich wrote:
> > > > This change doesn't seem to affect that, but what is the
> > > > minimum
> > > > supported s390x qemu host? z900?
> > > 
> > > Possibly z990, if I'm reading the gcc processor_flags_table[]
> > > correctly; 
> > > long-displacement-facility is definitely a minimum.
> > > 
> > > We probably should revisit what the minimum for TCG should be,
> > > assert those features at 
> > > startup, and drop the corresponding runtime tests.
> > 
> > If we consider the official IBM support statement:
> > 
> > https://www.ibm.com/support/pages/system/files/inline-files/IBM%20Mainframe%20Life%20Cycle%20History%20V2.10%20-%20Sept%2013%202022_1.pdf
> > 
> > ... that would mean that the z10 and all older machines are not
> > supported anymore.
> 
> Thanks for the pointer.  It would appear that z114 exits support at
> the end of this month, 
> which would leave z12 as minimum supported cpu.
> 
> Even assuming z196 gets us extended-immediate, general-insn-
> extension, load-on-condition, 
> and distinct-operands, which are all quite important to TCG, and
> constitute almost all of 
> the current runtime checks.
> 
> The other metric would be matching the set of supported cpus from the
> set of supported os 
> distributions, but I would be ready to believe z196 is below the
> minimum there too.
> 
> 
> r~

I think it should be safe to raise the minimum required hardware for
TCG to z196:

* The oldest supported RHEL is v7, it requires z196:

https://access.redhat.com/product-life-cycles/
https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/installation_guide/chap-installation-planning-s390

* The oldest supported SLES is v12, it requires z196:

https://www.suse.com/de-de/lifecycle/
https://documentation.suse.com/sles/12-SP5/html/SLES-all/cha-zseries.html

* The oldest supported Ubuntu is v16.04, it requires zEC12+:
https://wiki.ubuntu.com/S390X

Best regards,
Ilya