On 23/05/2021 02:46, BALATON Zoltan wrote:
On Sat, 22 May 2021, BALATON Zoltan wrote:
On Sat, 22 May 2021, BALATON Zoltan wrote:
On Sat, 22 May 2021, Alexey Kardashevskiy wrote:
VOF itself does not prints anything in this patch.
However it seems to be needed for linux as the first thing it does
seems to be getting /chosen/stdout and calls exit if it returns
nothing. So I'll need this at least for linux. (I think MorphOS may
also query it to print a banner or some messages but not sure it
needs it, at least it does not abort right away if not found.)
but to see Linux output do I need a stdout in VOF or it will just
open the serial with its own driver and use that?
So I'm not sure what's the stdout parts in the current vof patch
does and if I need that for anything. I'll try to experiment with
it some more but fixing the ld and Kconfig seems to be enough to
get it work for me.
So for the client to print something, /chosen/stdout needs to have a
valid ihandle.
The only way to get a valid ihandle is having a valid phandle which
vof_client_open() can open.
A valid phandle is a phandle of any node in the device tree. On
spapr we pick some spapr-vty, open it and store in /chosen/stdout.
From this point output from the client can be seen via a tracepoint.
I've got it now. Looking at the original firmware device tree dump:
https://osdn.net/projects/qmiga/wiki/SubprojectPegasos2/attach/PegasosII_OFW-Dump.txt
I see that /chosen/stdout points to "screen" which is an alias to
/bootconsole. Just adding an empty /bootconsole node in the device
tree and vof_client_open_store() that as /chosen/stdout works and I
get output via vof_write traces so this is enough for now to test
Linux. Properly connecting a serial backend can thus be postponed.
Using /failsafe instead of /bootconsole is even better because Linux
then adds console=ttyS0 to the bootargs by default as it knows that's a
serial port.
When linux boots so far that it can use whatever is passed in "console="
- the client interface is done pretty much and the output happens
without it.
So with this the Linux kernel does not abort on the first device tree
access but starts to decompress itself then the embedded initrd and
crashes at calling setprop:
[...]
vof_client_handle: setprop
Thread 4 "qemu-system-ppc" received signal SIGSEGV, Segmentation fault.
(gdb) bt
#0 0x0000000000000000 in ()
#1 0x0000555555a5c2bf in vof_setprop
(vof=0x7ffff48e9420, vallen=4, valaddr=<optimized out>,
pname=<optimized out>, nodeph=8, fdt=0x7fff8aaff010, ms=0x5555564f8800)
at ../hw/ppc/vof.c:308
#2 0x0000555555a5c2bf in vof_client_handle
(nrets=1, rets=0x7ffff48e93f0, nargs=4, args=0x7ffff48e93c0,
service=0x7ffff48e9460 "setprop",
vof=0x7ffff48e9420, fdt=0x7fff8aaff010, ms=0x5555564f8800) at
../hw/ppc/vof.c:842
#3 0x0000555555a5c2bf in vof_client_call
(ms=0x5555564f8800, vof=vof@entry=0x55555662a3d0,
fdt=fdt@entry=0x7fff8aaff010, args_real=args_real@entry=23580472)
at ../hw/ppc/vof.c:935
loooks like it's trying to set /chosen/linux,initrd-start:
(gdb) up
#1 0x0000555555a5c2bf in vof_setprop (vof=0x7ffff48e9420, vallen=4,
valaddr=<optimized out>, pname=<optimized out>, nodeph=8,
fdt=0x7fff8aaff010, ms=0x5555564f8800) at ../hw/ppc/vof.c:308
308 if (!vmc->setprop(ms, nodepath, propname, val, vallen)) {
(gdb) p nodepath
$1 = "/chosen\000\060/rPC,750CXE/", '\000' <repeats 234 times>
(gdb) p propname
$2 =
"linux,initrd-start\000linux,initrd-end\000linux,cmdline-timeout\000bootarg"
(gdb) p val
$3 = <optimized out>
I think I need the callback for setprop in TYPE_VOF_MACHINE_IF. I can
copy spapr_vof_setprop() but some explanation on why that's needed
might help. Ciould I just do fdt_setprop in my callback as
vof_setprop() would do without a machine callback or is there some
special handling needed for these properties?
Just returning true from the setprop callback of the VofMachineIfClass
for now to see what it would do and then it gets to all the way of
calling quiesce. Unfortunately it then tries to call prom_printf on
Pegasos2 as seen here:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/arch/powerpc/kernel/prom_init.c?h=v4.14.233#n3261
which does not work because I have to shut down vhyp at quiesce
What is vhyp and why do you have to shut it down?
otherwise it trips an assert on writing sdr1 (and may also interfere
with the guest's usage of syscalls).
Where is that assert?
I am a bit lost here. Nothing in the current VOF should touch any actual
device, it prints via tracepoints or (with that additional patch) to a
chardev backend.
So I need a way to not generate an
exception if the guest calls back into OF after quiesce. A hacky
solution is to patch out the sc 1 or _prom_entry point to just return
after quiesce but maybe a better way is needed such as a switch in
vof.bin that it checks before doing a syscall. Other than this problem
it seems to work for the most part so maybe making the _prom_entry check
some global value that I can set from quiesce to stop it doing syscalls
and just return would be the simplest way to avoid this crash in Linux
and not need a special version of vof for pegasos2. (MorphOS does not
seem to call OF after quiesce which seems safer to do anyway, don't know
why Linux does that. It could just print that one line before quiesce
and then it would work, unfortunately that's not what they did.)
quiesce is supposed to wait until ongoing DMA is finished (or something
like that), it was (people say) a request from Apple back then and was
never really architected.
--
Alexey
