[PATCH] Revert "powerpc/64s: machine check interrupt update NMI accounting"

[Michal Suchanek]

This reverts commit 116ac378bb3ff844df333e7609e7604651a0db9d.

This commit causes the kernel to oops and reboot when injecting a SLB
multihit which causes a MCE.

Before this commit a SLB multihit was corrected by the kernel and the
system continued to operate normally.

cc: sta...@vger.kernel.org
Fixes: 116ac378bb3f ("powerpc/64s: machine check interrupt update NMI 
accounting")
Signed-off-by: Michal Suchanek <msucha...@suse.de>
---
 arch/powerpc/kernel/mce.c   |  7 -------
 arch/powerpc/kernel/traps.c | 18 +++---------------
 2 files changed, 3 insertions(+), 22 deletions(-)

diff --git a/arch/powerpc/kernel/mce.c b/arch/powerpc/kernel/mce.c
index ada59f6c4298..2e13528dcc92 100644
--- a/arch/powerpc/kernel/mce.c
+++ b/arch/powerpc/kernel/mce.c
@@ -591,14 +591,10 @@ EXPORT_SYMBOL_GPL(machine_check_print_event_info);
 long notrace machine_check_early(struct pt_regs *regs)
 {
        long handled = 0;
-       bool nested = in_nmi();
        u8 ftrace_enabled = this_cpu_get_ftrace_enabled();
 
        this_cpu_set_ftrace_enabled(0);
 
-       if (!nested)
-               nmi_enter();
-
        hv_nmi_check_nonrecoverable(regs);
 
        /*
@@ -607,9 +603,6 @@ long notrace machine_check_early(struct pt_regs *regs)
        if (ppc_md.machine_check_early)
                handled = ppc_md.machine_check_early(regs);
 
-       if (!nested)
-               nmi_exit();
-
        this_cpu_set_ftrace_enabled(ftrace_enabled);
 
        return handled;
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index d1ebe152f210..7853b770918d 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -827,19 +827,7 @@ void machine_check_exception(struct pt_regs *regs)
 {
        int recover = 0;
 
-       /*
-        * 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).
-        *
-        * This is silly. The BOOK3S_64 should just call a different function
-        * rather than expecting semantics to magically change. Something
-        * like 'non_nmi_machine_check_exception()', perhaps?
-        */
-       const bool nmi = !IS_ENABLED(CONFIG_PPC_BOOK3S_64);
-
-       if (nmi) nmi_enter();
+       nmi_enter();
 
        __this_cpu_inc(irq_stat.mce_exceptions);
 
@@ -865,7 +853,7 @@ void machine_check_exception(struct pt_regs *regs)
        if (check_io_access(regs))
                goto bail;
 
-       if (nmi) nmi_exit();
+       nmi_exit();
 
        die("Machine check", regs, SIGBUS);
 
@@ -876,7 +864,7 @@ void machine_check_exception(struct pt_regs *regs)
        return;
 
 bail:
-       if (nmi) nmi_exit();
+       nmi_exit();
 }
 
 void SMIException(struct pt_regs *regs)
-- 
2.28.0