Re: [REGRESSION][BISECTED] Early boot hangs since f0551af02130

[Thomas Gleixner <tglx@linutronix.de>]

On Fri, Jul 26 2024 at 00:01, Christian Heusel wrote:
> Sorry for causing some confusion on that part and I hope the above
> outputs help with debugging this issue!

Not really. The issue is completely unclear and nothing makes any sense
here.

The only difference is the resulting number of possible CPUs.

[    0.026516] CPU topo: Allowing 4 present CPUs plus 12 hotplug CPUs

versus:

[    0.025251] CPU topo: Allowing 4 present CPUs plus 0 hotplug CPUs

which really should not make any difference because the 1300X has only 4
CPUs.

So the bisected commit is the messenger for some other problem
presumably in the IOMMU area which is just papered over when there are
12 possible hotplug CPUs enumerated.

So in theory the same problem should happen with a pre 6.9 kernel and
'nr_cpus=4' on the kernel command line. Can you please verify?

Another data point to be evaluated is whether booting the unmodified
6.10+ kernel with 'nointremap' instead of 'iommu=off' on the command
line makes the machine boot as well.

Thanks,

        tglx