On Tue, Jun 27, 2023 at 1:24 PM Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk
<mailto:mark.cave-ayland@ilande.co.uk>> wrote:
On 27/06/2023 11:28, Howard Spoelstra wrote:
> On Tue, Jun 27, 2023 at 10:15 AM Mark Cave-Ayland
<mark.cave-ayland@ilande.co.uk <mailto:mark.cave-ayland@ilande.co.uk>
> <mailto:mark.cave-ayland@ilande.co.uk
<mailto:mark.cave-ayland@ilande.co.uk>>> wrote:
>
> On 26/06/2023 14:35, Cédric Le Goater wrote:
>
> > On 6/23/23 14:37, Cédric Le Goater wrote:
> >> On 6/23/23 11:10, Peter Maydell wrote:
> >>> On Fri, 23 Jun 2023 at 09:21, Nicholas Piggin <npiggin@gmail.com
<mailto:npiggin@gmail.com>
> <mailto:npiggin@gmail.com <mailto:npiggin@gmail.com>>> wrote:
> >>>>
> >>>> ppc has always silently ignored access to real (physical)
addresses
> >>>> with nothing behind it, which can make debugging difficult at
times.
> >>>>
> >>>> It looks like the way to handle this is implement the
transaction
> >>>> failed call, which most target architectures do. Notably not
x86
> >>>> though, I wonder why?
> >>>
> >>> Much of this is historical legacy. QEMU originally had no
> >>> concept of "the system outside the CPU returns some kind
> >>> of bus error and the CPU raises an exception for it".
> >>> This is turn is (I think) because the x86 PC doesn't do
> >>> that: you always get back some kind of response, I think
> >>> -1 on reads and writes ignored. We added the
do_transaction_failed
> >>> hook largely because we wanted it to give more accurate
> >>> emulation of this kind of thing on Arm, but as usual with new
> >>> facilities we left the other architectures to do it themselves
> >>> if they wanted -- by default the behaviour remained the same.
> >>> Some architectures have picked it up; some haven't.
> >>>
> >>> The main reason it's a bit of a pain to turn the correct
> >>> handling on is because often boards don't actually implement
> >>> all the devices they're supposed to. For a pile of legacy Arm
> >>> boards, especially where we didn't have good test images,
> >>> we use the machine flag ignore_memory_transaction_failures to
> >>> retain the legacy behaviour. (This isn't great because it's
> >>> pretty much going to mean we have that flag set on those
> >>> boards forever because nobody is going to care enough to
> >>> investigate and test.)
> >>>
> >>>> Other question is, sometimes I guess it's nice to avoid
crashing in
> >>>> order to try to quickly get past some unimplemented MMIO.
Maybe a
> >>>> command line option or something could turn it off? It should
> >>>> probably be a QEMU-wide option if so, so that shouldn't hold
this
> >>>> series up, I can propose a option for that if anybody is
worried
> >>>> about it.
> >>>
> >>> I would not recommend going any further than maybe setting the
> >>> ignore_memory_transaction_failures flag for boards you don't
> >>> care about. (But in an ideal world, don't set it and deal with
> >>> any bug reports by implementing stub versions of missing
devices.
> >>> Depends how confident you are in your test coverage.)
> >>
> >> It seems it broke the "mac99" and powernv10 machines, using the
> >> qemu-ppc-boot images which are mostly buildroot. See below for
logs.
> >>
> >> Adding Mark for further testing on Mac OS.
> >
> >
> > Mac OS 9.2 fails to boot with a popup saying :
> > Sorry, a system error occured.
> > "Sound Manager"
> > address error
> > To temporarily turn off extensions, restart and
> > hold down the shift key
> >
> >
> > Darwin and Mac OSX look OK.
>
> My guess would be that MacOS 9.2 is trying to access the sound chip
registers which
> isn't implemented in QEMU for the moment (I have a separate screamer
branch
> available, but it's not ready for primetime yet). In theory they
shouldn't be
> accessed at all because the sound device isn't present in the OpenBIOS
device tree,
> but this is all fairly old stuff.
>
> Does implementing the sound registers using a dummy device help at
all?
>
>
> My uneducated guess is that you stumbled on a longstanding, but
intermittently
> occurring, issue specific to Mac OS 9.2 related to sound support over USB in
Apple
> monitors.
I'm not sure I understand this: are there non-standard command line options
being
used here other than "qemu-system-ppc -M mac99 -cdrom macos92.iso -boot d"?
It must be my windows host ;-)
qemu-system-ppc.exe -M mac99,via=pmu -cdrom C:\mac-iso\9.2.2.iso -boot d -L
pc-bios
crashes Mac OS with an address error. (with unpatched and patched builds).