Hello Christophe,

I was able to reduce the patch.

The following modification is responsible for the boot issue:

diff -rupN a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c

--- a/arch/powerpc/kernel/interrupt.c	2025-12-09 06:57:20.717347165 +0100
+++ b/arch/powerpc/kernel/interrupt.c	2025-12-09 10:24:37.357301725 +0100

@@ -38,7 +38,7 @@ static inline bool exit_must_hard_disabl
 #else
 static inline bool exit_must_hard_disable(void)
 {
-	return false;
+	return true;
 }
 #endif

- - -

After reverting this modification, the kernel boots without any problems.

Please check this modification.

Thanks,
Christian