[Bug 295528] FreeBSD 15.1-RC1: freebsd-update upgrade from 15.0-RELEASE triggers boot loop / Kernel Panic on systems with amdgpu (drm-66-kmod) due to ABI mismatch during stage 1 reboot

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=295528

            Bug ID: 295528
           Summary: FreeBSD 15.1-RC1: freebsd-update upgrade from
                    15.0-RELEASE triggers boot loop / Kernel Panic on
                    systems with amdgpu (drm-66-kmod) due to ABI mismatch
                    during stage 1 reboot
           Product: Base System
           Version: 15.1-RELEASE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: bin
          Assignee: bugs@FreeBSD.org
          Reporter: jimmbird2068@gmail.com

Environment:
* OS: FreeBSD 15.0-RELEASE upgrading to 15.1-RC1 via freebsd-update.
* Hardware: AMD GPU (using drm-kmod and gpu-firmware-kmod).
* Storage: ZFS with Boot Environments (zroot).

Steps to reproduce:
1. Run `freebsd-update fetch`.
2. Run `freebsd-update upgrade -r 15.1-RC1`
2. Run `freebsd-update install` to install the stage 1 (new kernel).
4. Keep `kld_list="amdgpu"` active in /etc/rc.conf.
5. Reboot the system.

Expected behavior:
The system should boot into a text console using the new 15.1-RC1 kernel,
allowing the user to run the second stage of `freebsd-update install` and
upgrade userland packages (`pkg upgrade`) to resolve kernel module
dependencies.

Actual behavior:
During the boot process, the system attempts to load the old 15.0-compiled
`amdgpu.ko` module from /boot/modules/. Due to kernel ABI mismatch between 15.0
and 15.1-RC1, the kernel panics immediately ("loading kernel modules amdgpu" is
shown, screen blanks, and the machine enters an infinite boot loop). 

Workaround found:
Booting via LiveCD, importing the ZFS pool, and commenting out
`#kld_list="amdgpu"` in /etc/rc.conf allows the 15.1-RC1 kernel to boot
successfully into a text-only console to complete the upgrade.

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