[Linuxppc-users] hardware transactions on power9

[Benjamin Herrenschmidt]

On Mon, 2018-07-09 at 10:20 -0600, Steve Pittman wrote:
> Peter,
> 
> At https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html-single/7.5_release_notes/indexI see:
> 
>  Red Hat Enterprise Linux 7.5 is distributed with the kernel-alt packages, which include kernel version 4.14. This kernel version provides support for the following architectures:
> 64-bit ARM
> IBM POWER9 (little endian)
> IBM z Systems
> 
> Are you running the 4.14 kernel from the kernal-alt packages?  If not, you do not have full RHEL 7.5 support for the POWER9 processor.

Ah you are running "PowerNV", which is native, with no hypervisor.

Due to POWER9 HW errata, we currently don't support HW Transactional
Memory in that mode. We have some support to use TM in a VM but not
bare metal.

Cheers,
Ben.

> Steve Pittman
> 
> 
> 
> From:        Peter Pirkelbauer <pirkelbauer at uab.edu>
> To:        linuxppc-users at lists.ozlabs.org
> Date:        07/09/2018 10:01 AM
> Subject:        [Linuxppc-users] hardware transactions on power9
> Sent by:        "Linuxppc-users" <linuxppc-users-bounces+skywalker=alum.mit.edu at lists.ozlabs.org>
> 
> 
> 
> Hi,
> 
> I am working on concurrent data structures built on top of hardware transactions.
> 
> Recently, I started testing on a Power 9 and ran into a problem with code that works well on a Power 8. When a transaction is started with __builtin_tbegin(0) the code terminates with an illegal instruction exception. (complete sample code is attached).
> 
> I used gcc 8.1 (compiled on the Power9) and I also tried gcc 7.3 to cross-compile on a power 8. The switch -mcpu=power9 was used on both systems.
> 
> The Power9 identifies as:
> processor    : 159
> cpu        : POWER9 (raw), altivec supported
> clock        : 3000.000000MHz
> revision    : 2.1 (pvr 004e 1201)
> 
> timebase    : 512000000
> platform    : PowerNV
> model        : 8335-GTG
> machine        : PowerNV 8335-GTG
> firmware    : OPAL
> MMU        : Radix
> 
> The Power 9 system runs Red Hat Enterprise Linux Server release 7.5 (Maipo) and uname gives:
> Linux cheaha02 4.14.0-49.2.2.el7a.ppc64le #1 SMP Fri Apr 27 15:37:52 UTC 2018 ppc64le ppc64le ppc64le GNU/Linux
> 
> I would appreciate any insights or pointers to relevant documentation.
> 
> Thank you,
> Peter
> 
> -----
> Peter Pirkelbauer, Ph.D.
> Assistant Professor
> http://iprogress.cis.uab.edu
> 
> Dept. of Computer Science
> 136 Campbell Hall
> University of Alabama at Birmingham
> 1300 University Boulevard, Birmingham, Alabama 35294-1170
> phone: (205) 934-8532
> 
> [attachment "testhtm.cc" deleted by Steve Pittman/San Francisco/IBM] 
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