From 116ac378bb3ff844df333e7609e7604651a0db9d Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Fri, 8 May 2020 14:34:03 +1000 Subject: powerpc/64s: machine check interrupt update NMI accounting machine_check_early() is taken as an NMI, so nmi_enter() is used there. machine_check_exception() is no longer taken as an NMI (it's invoked via irq_work in the case a machine check hits in kernel mode), so remove the nmi_enter() from that case. In NMI context, hash faults don't try to refill the hash table, which can lead to crashes accessing non-pinned kernel pages. System reset still has this potential problem. Signed-off-by: Nicholas Piggin [mpe: Drop change in show_regs() which breaks Book3E] Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20200508043408.886394-12-npiggin@gmail.com --- arch/powerpc/kernel/traps.c | 14 +++++++++++++- 1 file changed, 13 insertions(+), 1 deletion(-) (limited to 'arch/powerpc/kernel/traps.c') diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c index 3fca22276bb1..9f6852322e59 100644 --- a/arch/powerpc/kernel/traps.c +++ b/arch/powerpc/kernel/traps.c @@ -823,7 +823,19 @@ int machine_check_generic(struct pt_regs *regs) void machine_check_exception(struct pt_regs *regs) { int recover = 0; - bool nested = in_nmi(); + bool nested; + + /* + * BOOK3S_64 does not call this handler as a non-maskable interrupt + * (it uses its own early real-mode handler to handle the MCE proper + * and then raises irq_work to call this handler when interrupts are + * enabled). Set nested = true for this case, which just makes it avoid + * the nmi_enter/exit. + */ + if (IS_ENABLED(CONFIG_PPC_BOOK3S_64) || in_nmi()) + nested = true; + else + nested = false; if (!nested) nmi_enter(); -- cgit v1.2.3