From dc398a084d459f065658855454e09f2778f8c5cc Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 7 Oct 2022 00:04:11 +1000 Subject: [PATCH] powerpc/64s/interrupt: Perf NMI should not take normal exit path NMI interrupts should exit with EXCEPTION_RESTORE_REGS not with interrupt_return_srr, which is what the perf NMI handler currently does. This breaks if a PMI hits after interrupt_exit_user_prepare_main() has switched the context tracking to user mode, then the CT_WARN_ON() in interrupt_exit_kernel_prepare() fires because it returns to kernel with context set to user. This could possibly be solved by soft-disabling PMIs in the exit path, but that reduces our ability to profile that code. The warning could be removed, but it's potentially useful. All other NMIs and soft-NMIs return using EXCEPTION_RESTORE_REGS, so this makes perf interrupts consistent with that and seems like the best fix. Signed-off-by: Nicholas Piggin [mpe: Squash in fixups from Nick] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20221006140413.126443-3-npiggin@gmail.com --- arch/powerpc/kernel/exceptions-64s.S | 14 +++++++++++++- arch/powerpc/kernel/interrupt.c | 14 ++++++++------ 2 files changed, 21 insertions(+), 7 deletions(-) diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S index 5381a43e50fe..651c36b056bd 100644 --- a/arch/powerpc/kernel/exceptions-64s.S +++ b/arch/powerpc/kernel/exceptions-64s.S @@ -2357,9 +2357,21 @@ EXC_VIRT_END(performance_monitor, 0x4f00, 0x20) EXC_COMMON_BEGIN(performance_monitor_common) GEN_COMMON performance_monitor addi r3,r1,STACK_FRAME_OVERHEAD - bl performance_monitor_exception + lbz r4,PACAIRQSOFTMASK(r13) + cmpdi r4,IRQS_ENABLED + bne 1f + bl performance_monitor_exception_async b interrupt_return_srr +1: + bl performance_monitor_exception_nmi + /* Clear MSR_RI before setting SRR0 and SRR1. */ + li r9,0 + mtmsrd r9,1 + kuap_kernel_restore r9, r10 + + EXCEPTION_RESTORE_REGS hsrr=0 + RFI_TO_KERNEL /** * Interrupt 0xf20 - Vector Unavailable Interrupt. diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index 7bc93367de68..fc6631a80527 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -377,13 +377,15 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs) * CT_WARN_ON comes here via program_check_exception, so avoid * recursion. * - * Skip the assertion on PMIs to work around a problem caused by NMI - * PMIs incorrectly taking this interrupt return path, it's possible - * for this to hit after interrupt exit to user switches context to - * user. See also the comment in the performance monitor handler in - * exceptions-64e/s.S + * Skip the assertion on PMIs on 64e to work around a problem caused + * by NMI PMIs incorrectly taking this interrupt return path, it's + * possible for this to hit after interrupt exit to user switches + * context to user. See also the comment in the performance monitor + * handler in exceptions-64e.S */ - if (TRAP(regs) != INTERRUPT_PROGRAM && TRAP(regs) != INTERRUPT_PERFMON) + if (!IS_ENABLED(CONFIG_PPC_BOOK3E_64) && + TRAP(regs) != INTERRUPT_PROGRAM && + TRAP(regs) != INTERRUPT_PERFMON) CT_WARN_ON(ct_state() == CONTEXT_USER); kuap = kuap_get_and_assert_locked();