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


From: Christian Borntraeger
Subject: Re: [PATCH v3 02/13] tcg/s390x: Remove TCG_REG_TB
Date: Wed, 7 Dec 2022 22:20:53 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0



Am 07.12.22 um 21:40 schrieb Ilya Leoshkevich:
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:

We recently raised the minimum hardware for the Linux kernel to be z10, so that 
would be super-safe, but z196 is certainly a sane minimum.

* 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



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