Re: Does kvm_pr work on G5 mac with host kernel 6.12.xx ?

["Christophe Leroy (CS GROUP)" <chleroy@kernel.org>]

Le 15/06/2026 à 11:26, Andrew Randrianasulu a écrit :
> 
> 
> вс, 14 июн. 2026 г., 23:35 BALATON Zoltan <balaton@eik.bme.hu 
> <mailto:balaton@eik.bme.hu>>:

[...]

> 
>     But that's BookE e500 not the BookS POWER4 variant G5 you have so
>     KVM may
>     work differently on that and maybe it even has HV which probably works
>     better than PR. 
> 
> 
> oh yes, I noticed another "hidden" option in Kconfig about kvm pr on 
> E5500/E6500
> 
> It was hidden because I did not select such machine in config, I guess.
> 
> 
>     I think KVM was used on G4, e500 and newer POWER mostly
>     with HV but I'm not sure if KVM PR on G5 was ever well supported.
>     Did you
>     try running the same Linux version that you have on your host under
>     KVM PR
>     first to verify that at least that works? I think that's where
>     everybody
>     should start with KVM before trying to boot other guest OSes.
> 
>      >> So considering the above, what may work is if you run a 32 bit
>     ppc kernel
>      >> (G4 version) on your G5 for the host not using it as 64 bit
>     instead of
>      >> ppc64 kernel and try a guest kernel that detects G5 CPU and
>     knows how to
>      >> handle the different cache line size.
>      >
>      >
>      > Are you saying 32bit *Linux* ppc kvm as host can handle 64bit
>     guest kernel ?
> 
>     No I meant trying a 32 bit host with 32 bit guest but the cache line
>     size
>     issue may still get in the way so maybe this does not help but for
>     debugging may worth a try.
> 
>      > I am not ever sure firmware here can load 32bit ppc Linux .. I'll
>     try of
>      > course.
> 
>     Since G5 is backwards compatible with PPC32 maybe it should work but I
>     know nothing about real PowerPC machines.
> 
>      > Or find and fix the emulation of
>      >> different instructions on ppc64 in Linux KVM when running 32 bit
>     ppc code
>      >> on 64 but host. There supposed to be some support for that but
>     maybe it's
>      >> broken or never finished.
> 
> 
> I found this email msg today:
> 
> 
> https://lkml.iu.edu/1605.1/03841.html <https:// 
> eur01.safelinks.protection.outlook.com/? 
> url=https%3A%2F%2Flkml.iu.edu%2F1605.1%2F03841.html&data=05%7C02%7Cchristophe.leroy2%40cs-soprasteria.com%7C5e49653ba80147cc12e808decac03273%7C8b87af7d86474dc78df45f69a2011bb5%7C0%7C0%7C639171124039051598%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=7gxjETKFSAMFjcnBQUuYcFHR2OE7b3W%2FGMRdHWF9X0Q%3D&reserved=0>
> 
> checked
> 
> linux-6.12.92/arch/powerpc/kvm/emulate.c and there seems to be ifdef 
> only for
> 
> #ifdef CONFIG_PPC_BOOK3S                                                
>                             kvmppc_core_queue_program(vcpu, SRR1_PROGTRAP);
> #else                                                                    
>                            kvmppc_core_queue_program(vcpu,              
>                                arch.shared->esr | ESR_PTR);
> #endif
> 
> 
> may be this ifdef should include CONFIG_PPC_BOOK3S_64 as well ?

I don't understand what you mean.

CONFIG_PPC_BOOK3S is defined as:

config PPC_BOOK3S
	def_bool y
	depends on PPC_BOOK3S_32 || PPC_BOOK3S_64

Christophe