PowerMac G5 hangs/crashes on boot: 10.2, 11.0-RCx

[Mark Millard]

On 2016-Sep-11, at 12:04 PM, Krzysztof Parzyszek <kristof at swissmail.org> wrote:

> On 9/10/2016 7:12 PM, Mark Millard wrote:
>> 
>> Your report that you have some sort of failure after booting during the likes of buildkernel is new as far as I know. Sending the list (and/or a bugzilla report) about the failure mode and related information may be appropriate and help in the future. (May be I missed an already existing report.)
> 
> I think the issues with hangs are related to the temperature sensors.  I was getting console messages that the media temp sensor was reporting 120C! I realized that as I replaced the hard drive, I changed the position of the drive in a way that exposed the sensor to the wind from the fans (it used to be angled a bit). Following this line of thought, I stuck a piece of paper in front of the sensor and things seem to work. At least work better than before. I have ordered a replacement sensor from eBay, so hopefully that problem will go away.
> 
> Regarding your "hack": it works perfectly! So far, my system (10.3 at the moment) has booted every single time, no exceptions, traps, unexpected conditions. This is too good to remain as a "hack". I have no experience debugging the kernel and I don't know ABI the OFW follows, but I wouldn't mind digging a bit deeper into it, if someone shared some pointers.
> 
> This is all with powerpc64.
> 
> I'll try checking if it helps with 11.0 next.
> 
> -Krzysztof

One of the worries about the hack is that other PowerMac G5 variants than I and you have tested on might behave differently. After all your experiments with my hack you might want to add notes about the results to the bugzilla report https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205458 . It would be good to be explicit about the type of PowerMac G5(s). Various folks believe that the amount of RAM contributes to the issue based on their observations so reporting that is likely important.

I likely need to add notes about the two types of PowerMac G5 variants and the RAM configurations that my activities involved. (The list history has this information but it would be a pain to find.)


Going in a different direction. . .

If you are willing you might want to help Nathan Whitehorn with testing that I'll not be able to do until I get access to the powerpc64's (and powerpc's) again.

See, for example, https://lists.freebsd.org/pipermail/freebsd-ppc/2016-June/008275.html :

>> Author: nwhitehorn
>> Date: Sun Jun 26 18:43:42 2016
>> New Revision: 302214
>> URL:
>> https://svnweb.freebsd.org/changeset/base/302214
>>
>>
>> Log:
>>    Enter 64-bit mode as early as possible in the 64-bit PowerPC boot sequence.
>>    Most of the effect of setting MSR[SF] is that the CPU will stop ignoring
>>    the high 32 bits of registers containing addresses in load/store
>>    instructions. As such, the kernel was setting it only when it began to
>>    need access to high memory. MSR[SF] also affects the operation of some
>>    conditional instructions, however, and so setting it at late times could
>>    subtly break code at very early times. This fixes use of the FDT mode in
>>    loader, and FDT boot more generally, on 64-bit PowerPC systems.
>>    
>>    Hardware provided by: IBM LTC
>>    Approved by: re (kib)
>>
>> Modified:
>>    head/sys/powerpc/aim/aim_machdep.c
>>    head/sys/powerpc/aim/locore64.S

In addition he wrote in the specific message:

> One thing it would be great to have some testing on after this change is 
> the FDT layer in loader. If you set usefdt=1 from the loader prompt, 
> loader will distill the OF device tree into an FDT and then stop Open 
> Firmware completely before transferring control to FreeBSD. This should 
> avoid any possible problems accessing Open Firmware from the kernel, as 
> well as making boot a little faster.

(I had temporarily lost access to the powerpc64's (and powerpc's) already.)

I expect that he would like some testing without my hack present that eliminates. . .

>      "mtsprg0 %1\n\t"
> and
>      "r"(ofmsr[1]),

If there are still problems then testing with my hack present would be a good idea as well.

This activity might produce more material appropriate to report at https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205458 .

===
Mark Millard
markmi at dsl-only.net