powerpc/64s: machine check interrupt update NMI accounting (116ac378) · Commits · 戴 / test

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 <npiggin@gmail.com> [mpe: Drop change in show_regs() which breaks Book3E] Signed-off-by:

Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20200508043408.886394-12-npiggin@gmail.com

arch/powerpc/kernel/mce.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -574,6 +574,9 @@ EXPORT_SYMBOL_GPL(machine_check_print_event_info);
		long machine_check_early(struct pt_regs *regs)
		{
		long handled = 0;
		bool nested = in_nmi();
		if (!nested)
		nmi_enter();

		hv_nmi_check_nonrecoverable(regs);

		@@ -582,6 +585,10 @@ long machine_check_early(struct pt_regs *regs)
		*/
		if (ppc_md.machine_check_early)
		handled = ppc_md.machine_check_early(regs);

		if (!nested)
		nmi_exit();

		return handled;
		}

arch/powerpc/kernel/traps.c

+13 −1

Original line number	Diff line number	Diff line
		@@ -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();

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