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A kernel panic is observed when handling machine check exceptions from real mode. BUG: Unable to handle kernel data access on read at 0xc00000006be21300 Oops: Kernel access of bad area, sig: 11 [#1] MSR: 8000000000001003 <SF,ME,RI,LE> CR: 88222248 XER: 00000005 CFAR: c00000000003ffc4 DAR: c00000006be21300 DSISR: 40000000 IRQMASK: 0 NIP [c000000000029e40] arch_irq_work_raise+0x10/0x70 LR [c00000000003ffc8] machine_check_queue_event+0xa8/0x150 Call Trace: [c0000000179d3c70] [c00000000003ff64] machine_check_queue_event+0x44/0x150 [c0000000179d3d30] [c0000000000084e0] machine_check_early_common+0x1f0/0x2c0 The crash occurs because arch_irq_work_raise() calls preempt_disable() from machine check exception (MCE) handlers running in real mode. In this context, accessing the preempt_count can fault, leading to the panic. The preempt_disable()/preempt_enable() pair in arch_irq_work_raise() was originally added by commit0fe1ac48be("powerpc/perf_event: Fix oops due to perf_event_do_pending call") to avoid races while raising irq work from exception context. Later, commit471ba0e686("irq_work: Do not raise an IPI when queueing work on the local CPU") added preemption protection in irq_work_queue() path, while commit20b876918c("irq_work: Use per cpu atomics instead of regular atomics") added equivalent protection in irq_work_queue_on() before reaching arch_irq_work_raise(): irq_work_queue() / irq_work_queue_on() -> preempt_disable() -> __irq_work_queue_local() -> irq_work_raise() -> arch_irq_work_raise() As a result, callers other than mce_irq_work_raise() already execute with preemption disabled, making the additional preempt_disable()/preempt_enable() pair in arch_irq_work_raise() redundant. The arch_irq_work_raise() function executes in NMI context when called from MCE handler. Hence we will not be preempted or scheduled out since we are in NMI context with MSR[EE]=0. Therefore, it is safe to remove the preempt_disable()/preempt_enable() calls from here. Remove it to avoid accessing preempt_count from real mode context. Fixes:cc15ff3275("powerpc/mce: Avoid using irq_work_queue() in realmode") Suggested-by: Mahesh Salgaonkar <mahesh@linux.ibm.com> Acked-by: Shrikanth Hegde <sshegde@linux.ibm.com> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> Signed-off-by: Sayali Patil <sayalip@linux.ibm.com> [Maddy: Fixed the commit title] Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com> Link: https://patch.msgid.link/20260513081413.222490-1-sayalip@linux.ibm.com