Re: [Buildroot] [PATCH 1/3] configs/qemu: Add a ppc64le-powernv8 configuration

["Cédric Le Goater" <clg@kaod.org>]

Hello Thomas,

> Thanks, entire patch series applied. One small change was done: add
> appropriate entries to the DEVELOPERS file, so that we know who to
> contact for those defconfigs :-) Especially if our Gitlab CI
> infrastructure detects build issues, you will be notified.

sure. I have a generated set here :

   https://github.com/legoater/qemu-ppc-boot/tree/main/buildroot

that I use for non regression on QEMU PPC.

> Since you are a PowerPC expert, I'd like to take this opportunity to
> ask you about the toolchains we're providing at
> https://toolchains.bootlin.com/. For the moment for PowerPC, we are
> providing the following toolchains:
> 
> powerpc-440fp, not tested

The bamboo machine uses a 440EP CPU implementation, which has a
floating point unit.
     
> powerpc64-e5500, tested with qemu_ppc64_e5500_defconfig
> powerpc64-e6500, not tested

e6500 is nearly the same CPU as e5500. AFAIK, the main differences
are altivec instructions and more HV support for guest translations.

More info here :

   https://www.linux-kvm.org/page/E500_virtual_CPU_specification

> powerpc64le-power8, tested with qemu_ppc64le_pseries_defconfig
> powerpc64-power8, tested with qemu_ppc64_pseries_defconfig
> powerpc-e300c3, not tested
> powerpc-e500mc, not tested

you could use the 32bit ppce500 machine for that.

> I suppose I could now test the powerpc-440fp toolchain with the
> qemu_ppc_bamboo_defconfig you have added. Is that correct?

yes.
  
> What about the other toolchain configurations? Is there some matching
> Qemu emulation?>
> And generally speaking, does this selection of PowerPC architecture
> variants make sense to offer pre-compiled toolchains? For quite a

Here is a quick status of machine/CPUs that QEMU implements :

* prep

   prep: 604 CPU (we might remove 601-603 CPUs)

* embedded

   ref405ep: 405EP (user space segfaults but same image works on 44x CPUs
                    I hope to get that one fixed by QEMU 7.0 )
   bambo:    440FP
   sam460ex: 460EP is very much like the 440fp

* Mac

   g3beige:  G3 (or 75x CPU) family
   mac99:    G4 (7400 7410 7441 7447 7448 7450 7451 7455 7457) family

* book3e 32bit:

   ppce500:   e500mc
   mpc8544ds: mpc8544

* book3e 64bit:

   ppce500 (KVM): e5500, e6500
   
* book3s 64bit (para virtualized and baremetal):

   mac99: PPC970
   pseries (BE only): PPC970, PPC970mp, POWER5+
   pseries (LE, BE and KVM) : POWER7, POWER8, POWER9, POWER10
   powernv: POWER8, POWER9, POWER10

Most of the attention is on book3s 64bit CPUs. MAC emulation is well
maintained. Embedded world is not.

> while, we've had requests for other PowerPC variants:
> https://github.com/bootlin/toolchains-builder/issues/2. Your input
> would be very welcome :-)

OK. I will take a look.

Thanks,

C.
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