ppc July 2021

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2 discussions

Power support for Fedora beyond IBM POWER (e.g. Libre-SOC)?
by Robert Scheck 10 Dec '21

10 Dec '21

Good evening, my interest in Power architecture got started when I read in February 2020 about the new open license model on a well-known German news ticker [1]. I attended the OpenPOWER Virtual Summit 2020 North America [2] in September and heard there the first time about Libre-SOC [3], previously also known as Libre-RISCV SoC [4] before they switched from RISC-V to Power. During FOSDEM 2021, I noticed their LibreSOC Project stand [5] and asked multiple beginner questions, which Luke Kenneth Casson Leighton (on Cc) nicely took care of (thank you!). Given an idea is a Power-based SBC [6], I wondered whether I could just run a Fedora for ppc64le (which seems to currently target POWER8 LE and later), on it. Unfortunately Luke's answer was no, because LibreSOC won't support VSX [7], which are IBM's SIMD (six hundred?) instructions, but the LibreSOC Project plans to have Simple-V Vectorisation according to their FOSDEM talk [8]. Note, the A2O POWER processor core [9] doesn't support VSX, too (same seems to apply to A2I and Microwatt, but they're either POWER7 or likely not powerful enough for typical PC usage anyway -> outside of Fedora's target?). Trying to follow the path on how to get Fedora for ppc64le to a "POWER-Pi", I had to learn that glibc developers seem to treat IBM POWER9 strictly equal to ABI rules rather handling the different features more fine granulated. My understanding here might be imprecise or wrong, this is what I understood and I'm no expert at this topic. Nevertheless I'm trying to precise it a bit more: The IBM Power ISA Version 3.1 [10] specifies on page 8 compliancy subsets, where the Linux Compliancy Subset (LCS) is explained on page 10 ff. Page 11 refers specifically to the "Scalar Float Optional Features" and mentions in the first row of the table VSX. However what seems to be implemented e.g. in glibc is something like "#ifdef POWER9" rather "#ifdef HARDWAREFEATURE", which effectively makes VSX support mandatory rather optional. Given the only publicly known modern implementor of VSX right now, not on an EOL schedule, seems to be IBM's POWER9, it would from my point of view be helpful that VSX support in at least glibc is made optional. When asking whether the new glibc-hwcaps [11] could be a solution, Luke's answer read for me like a conditional "yes", because at least VSX should be covered by glibc-hwcaps then (again, same as above...my understanding, I'm still no expert here). But this is why I'm Cc-ing here Florian Weimer, who implemented [12] this new glibc feature. I'm not sure if Florian is the right person for this topic at all, but maybe he knows the right people? :) Finally, to close the circle to the subject of my mail: (how) can we reach Power support for Fedora (and other mainstream Linux distributions) beyond IBM POWER (e.g. Libre-SOC)? [1] https://www.heise.de/newsticker/meldung/Prozessor-ISA-Power-OpenPower-Found… [2] https://openpowerfoundation.org/events/openpower-summit-2020-north-america/ [3] https://libre-soc.org/ [4] http://lists.libre-riscv.org/pipermail/libre-riscv-dev/2019-October/thread.… [5] https://stands.fosdem.org/stands/the_libresoc_project__a_hybrid_3d_cpu_vpu_… [6] https://libre-soc.org/22nm_PowerPI/ [7] https://en.wikipedia.org/wiki/AltiVec#VSX_.28Vector_Scalar_Extension.29 [8] https://fosdem.org/2021/schedule/event/the_libresoc_project_simple_v_vector… [9] https://openpowerfoundation.org/a-deep-dive-into-a2i-and-a2o/ [10] https://ibm.ent.box.com/s/hhjfw0x0lrbtyzmiaffnbxh2fuo0fog0 [11] https://sourceware.org/pipermail/libc-announce/2021/000030.html [12] https://sourceware.org/pipermail/libc-alpha/2020-June/115250.html Regards, Robert

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Fw: Architecture "ppc64le" again in Fedora Copr
by Dan Horák 16 Jul '21

16 Jul '21

Forwarding the good news from the infra/copr team. Dan Date: Wed, 14 Jul 2021 16:25:46 +0200 From: Pavel Raiskup <praiskup(a)redhat.com> To: copr-devel(a)lists.fedorahosted.org Cc: Discussion of Fedora build system <buildsys(a)lists.fedoraproject.org> Subject: Architecture "ppc64le" again in Fedora Copr Hi all, I'm glad I can announce that we have again (native) support for ppc64le builds in Fedora Copr. Currently we have two Power8 boxes (in RDU): https://pagure.io/fedora-infrastructure/issue/9059 The ppc64le chroots were re-enabled, feel free to use them. I noticed several build failures caused by missing repodata in ppc64le chroots, please re-generate the repodata manually if you happen to see those problems. Happy building! Pavel

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ppc July 2021