[PATCH v2] powerpc/entry: Disable interrupts before irqentry_exit

[Shrikanth Hegde <sshegde@linux.ibm.com>]

Venkat reported a panic on powerpc-next tree where GENERIC_ENTRY has
been enabled.

kernel BUG at kernel/sched/core.c:7512!
NIP  preempt_schedule_irq+0x44/0x118
LR   dynamic_irqentry_exit_cond_resched+0x40/0x1a4
Call Trace:
 dynamic_irqentry_exit_cond_resched+0x40/0x1a4
 do_page_fault+0xc0/0x104
 data_access_common_virt+0x210/0x220

This happens since __do_page_fault ends up enabling the interrupts and
it could take significant time such that need_resched could be set. This
leads to schedule call in irqentry_exit leading to the bug.

There are many such irq handlers which enables the interrupts.
Fix it by disabling the irq before calling irqentry_exit. The same
pattern exists today in interrupt_exit_kernel_prepare.

Fixes: bee25f97ad24 ("powerpc: Enable GENERIC_ENTRY feature")
Reported-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Closes: https://lore.kernel.org/all/7904105b-9dfa-4efd-a5ef-bc0276ed255d@linux.ibm.com/
Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
---
This applies on top on powerpc/next tree.
base: 6ed60999d33d '("powerpc: Remove unused functions")'

v1->v2:
Leave those BUG_ON alone since they are tracking the register
state of userspace (Peter Zijlstra)
v1: https://lore.kernel.org/all/20260603095521.198267-1-sshegde@linux.ibm.com/

 arch/powerpc/include/asm/entry-common.h | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/include/asm/entry-common.h b/arch/powerpc/include/asm/entry-common.h
index de5601282755..fc636c42e89a 100644
--- a/arch/powerpc/include/asm/entry-common.h
+++ b/arch/powerpc/include/asm/entry-common.h
@@ -260,9 +260,10 @@ static inline void arch_interrupt_exit_prepare(struct pt_regs *regs)
 		 * AMR can only have been unlocked if we interrupted the kernel.
 		 */
 		kuap_assert_locked();
-
-		local_irq_disable();
 	}
+
+	/* irqentry_exit expects to be called with interrupts disabled */
+	local_irq_disable();
 }
 
 static inline void arch_interrupt_async_enter_prepare(struct pt_regs *regs)
-- 
2.47.3