Re: [Qemu-ppc] [OpenBIOS] Apple's BootX

[James Lyons]

On 01/30/2018 11:14 AM, Jd Lyons wrote:
> > On Jan 30, 2018, at 10:47 AM, Jd Lyons via OpenBIOS <address@hidden> wrote:
> >
> >
> >
> > > On Jan 30, 2018, at 9:10 AM, BALATON Zoltan <address@hidden> wrote:
> > >
> > > On Mon, 29 Jan 2018, Jd Lyons via OpenBIOS wrote:
> > > > Ok, with a little help for Paul at the kvm-ppc mailing list, it seems the issue 
> > > > maybe that the BootX or more likely mach_kernel it trying to write something to 
> > > > or probe for an L3 cache.
> > > With kvm could be but on TCG it doesn't seem that way. Enabling some SPR debug 
> > > options in target/ppc/translate_init.c I see this (with qemu git HEAD without 
> > > other patches):
> > >
> > > $ ppc-softmmu/qemu-system-ppc -cpu G4 -d int
> > > Write SPR 272 110 <= 07e00000
> > > Read SPR 287 11f => 000c0209
> > > Read SPR 25 019 => 07e00000
> > > Read SPR 25 019 => 07e00000
> > > Read SPR 287 11f => 000c0209
> > > Raise exception at fff08978 => 00000003 (40000000)
> > > Write SPR 273 111 <= 07df7ff0
> > > Write SPR 274 112 <= 20000004
> > > Read SPR 272 110 => 07e00000
> > > Read SPR 273 111 => 07df7ff0
> > > Read SPR 274 112 => 20000004
> > > Read SPR 26 01a => fff08978
> > > Read SPR 27 01b => 40000030
> > >
> > > $ ppc-softmmu/qemu-system-ppc -cpu 7447a -d int
> > > Write SPR 272 110 <= 07e00000
> > > Read SPR 287 11f => 80030102
> > > Read SPR 25 019 => 07e00000
> > > Read SPR 25 019 => 07e00000
> > > Read SPR 287 11f => 80030102
> > > Raise exception at fff08978 => 0000004e (00)
> > >
> > > So OpenBIOS gets unexpected exception very early right after reading the PVR so 
> > > maybe it's a problem in OpenBIOS before it gets to what you're describing. Is 
> > > this already fixed?
> > >
> > > Regards,
> > > BALATON Zoltan
> > >
> > > --
> > > OpenBIOS                 http://openbios.org/
> > > Mailinglist:  http://lists.openbios.org/mailman/listinfo
> > > Free your System - May the Forth be with you
> > It looks like in TCG mode that it tries to read these invalid spr’s
> >
> > 1018
> > 1011
> > 1016
> > 1012
> >
> > This doesn’t cause a halt, as the kernel boots.
> What I’m assuming is the kernel is trying to read the state of spr 1018 (r13), 
> but it can’t read it. It does seem to exist for the 7447a it’s value is just 
> zero( 0x00000000 ) and of course you can’t write anything there.
>
> I don’t think the kernel is trying to write anything there, I think it’s just 
> probing the state of the register to determine if the L3 cache exists. There 
> are just too many references to the r13 in the xun source for me to figure out 
> how to stop the kernel from trying to make a read here. Paul seems to suggest 
> it could be fixed in KVM, but it seems like I could fix it in Qemu if I knew 
> how to get Qemu to pass that spr( 1018 ) to the guest as readable with the 
> value 0x00000000.
>
> Would anyone be able to help me do that?
Ok, I tried like this:

spr_register_kvm(env, SPR_L3CR, "L3CR",
                     SPR_NOACCESS, SPR_NOACCESS,
                     &spr_read_generic, &spr_write_generic,
                     KVM_REG_PPC_L3CR, 0x00000000);

And I defined:

#define KVM_REG_PPC_L3CR    (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x3fa)

Not sure, that likely should be KVM_REG_SIZE_U32?

I always get confused by that, I'm assuming it should be U32, as it's a 
32bit register?

Tried it both ways, hoping KVM would allow a read at spr 1018, but no 
dice, system still hangs after Call Kernel! and I still get:

KVM: invalid SPR read: 1018

I'm running out of ideas.






> > --
> > OpenBIOS                 http://openbios.org/
> > Mailinglist:  http://lists.openbios.org/mailman/listinfo
> > Free your System - May the Forth be with you