Re: [PATCH] S390: Influence hwcaps/stfle via GLIBC_TUNABLES.

[Stefan Liebler <stli@linux.ibm.com>]

On 06.02.23 15:21, Florian Weimer wrote:
> * Stefan Liebler via Libc-alpha:
> 
>> This patch enables the option to influence hwcaps and stfle bits used
>> by the s390 specific ifunc-resolvers.  The currently x86-specific
>> tunable glibc.cpu.hwcaps is also used on s390x to achieve the task. In
>> addition the user can also set a CPU arch-level like z13 instead of
>> single HWCAP and STFLE features.
>>
>> Note that the tunable only handles the features which are really used
>> in the IFUNC-resolvers.  All others are ignored as the values are only
>> used inside glibc.  Thus we can influence:
>> - HWCAP_S390_VXRS (z13)
>> - HWCAP_S390_VXRS_EXT (z14)
>> - HWCAP_S390_VXRS_EXT2 (z15)
>> - STFLE_MIE3 (z15)
>>
>> The influenced hwcap/stfle-bits are stored in the s390-specific
>> cpu_features struct which also contains reserved fields for future
>> usage.
>>
>> The ifunc-resolvers and users of stfle bits are adjusted to use the
>> information from cpu_features struct.
>>
>> On 31bit, the ELF_MACHINE_IRELATIVE macro is now also defined.
>> Otherwise the new ifunc-resolvers segfaults as they depend on
>> the not yet processed_rtld_global_ro@GLIBC_PRIVATE relocation.
>> ---
> 
> I think you are updating all the right places.  You should probably push
> this as the hardware maintainer.
> 
> Thanks,
> Florian
> 

Sure. I've just committed the patch. Thanks for having a look at the patch.

Bye
Stefan