[Bug 2104297] Re: not able to install a Power9 bare metal with Ubuntu 25.04 Plucky

** Description changed:

+ [ Impact ]
+
+ In ppc64el kernels, loading modules without any
+ __patchable_function_entries section would fail due to a
+ zero size allocation of executable memory for ftrace trampolines.
+ This causes boot failures when trying to boot the kernel on IBM Power 9
+ systems. In particular becasue IBM Power 9 tries to load i40e at boot
+ time, which fails.
+
+ The bug was introduced by commit eec37961a56a which landed in v6.13-rc1,
+ which assumed all modules have traceable functions.
+
+ [ Fix ]
+
+ Apply the following patch:
+ - https://lore.kernel.org/all/wlscshbqan2svtqkz5xc6v47tzndfnsvge7h4lbfn67zoplekl@elt2oxwhrp6f/T/
+ which has not landed in linux-next yet.
+
+ [ Test Plan ]
+
+ Compile and boot test the kernel on a Power 9 bare metal machine.
+
+ [ Where problems could occur ]
+
+ The patch simply removes an if branch which handles (incorrectly) errors during
+ module loading on ppc64 systems. The regression potential therefore is
+ very low.
+
+ -----
+
Not able to netboot install a Power9 bare metal. It fails because it is
not detecting network, after that the system goes to shell/busybox

```
Begin: Waiting up to 180 secs for any network device to become available ... Failure: Network device did not appear in time
done.
dhcpcd-10.1.0 starting
dev: loaded udev
[ 188.277865] 8021q: 802.1Q VLAN Support v1.8
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
Sleeping 30 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 60 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 90 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 120 seconds before retrying getting a DHCP lease

-
BusyBox v1.37.0 (Ubuntu 1:1.37.0-4ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)
```

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https://bugs.launchpad.net/bugs/2104297

Title:
not able to install a Power9 bare metal with Ubuntu 25.04 Plucky

Status in The Ubuntu-power-systems project:
New
Status in linux package in Ubuntu:
New

Bug description:
[ Impact ]

In ppc64el kernels, loading modules without any
__patchable_function_entries section would fail due to a
zero size allocation of executable memory for ftrace trampolines.
This causes boot failures when trying to boot the kernel on IBM Power 9
systems. In particular becasue IBM Power 9 tries to load i40e at boot
time, which fails.

The bug was introduced by commit eec37961a56a which landed in v6.13-rc1,
which assumed all modules have traceable functions.

[ Fix ]

Apply the following patch:
- https://lore.kernel.org/all/wlscshbqan2svtqkz5xc6v47tzndfnsvge7h4lbfn67zoplekl@elt2oxwhrp6f/T/
which has not landed in linux-next yet.

[ Test Plan ]

Compile and boot test the kernel on a Power 9 bare metal machine.

[ Where problems could occur ]

The patch simply removes an if branch which handles (incorrectly) errors during
module loading on ppc64 systems. The regression potential therefore is
very low.

-----

Not able to netboot install a Power9 bare metal. It fails because it
is not detecting network, after that the system goes to shell/busybox

```
Begin: Waiting up to 180 secs for any network device to become available ... Failure: Network device did not appear in time
done.
dhcpcd-10.1.0 starting
dev: loaded udev
[ 188.277865] 8021q: 802.1Q VLAN Support v1.8
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
Sleeping 30 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 60 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 90 seconds before retrying getting a DHCP lease
dhcpcd-10.1.0 starting
dev: loaded udev
no valid interfaces found
exiting due to oneshot
aborting as link detection is disabled
dhcpcd exited
Sleeping 120 seconds before retrying getting a DHCP lease

BusyBox v1.37.0 (Ubuntu 1:1.37.0-4ubuntu1) built-in shell (ash)
Enter 'help' for a list of built-in commands.

(initramfs)
```

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