ACPI / APEI: Fix NMI notification handling

When removing and adding cpu 0 on a system with GHES NMI the following stack
trace is seen when re-adding the cpu:

WARNING: CPU: 0 PID: 0 at arch/x86/kernel/apic/apic.c:1349 setup_local_APIC+
Modules linked in: nfsv3 rpcsec_gss_krb5 nfsv4 nfs fscache coretemp intel_ra
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.0-rc6+ #2
Call Trace:
 dump_stack+0x63/0x8e
 __warn+0xd1/0xf0
 warn_slowpath_null+0x1d/0x20
 setup_local_APIC+0x275/0x370
 apic_ap_setup+0xe/0x20
 start_secondary+0x48/0x180
 set_init_arg+0x55/0x55
 early_idt_handler_array+0x120/0x120
 x86_64_start_reservations+0x2a/0x2c
 x86_64_start_kernel+0x13d/0x14c

During the cpu bringup, wakeup_cpu_via_init_nmi() is called and issues an
NMI on CPU 0.  The GHES NMI handler, ghes_notify_nmi() runs the
ghes_proc_irq_work work queue which ends up setting IRQ_WORK_VECTOR
(0xf6).  The "faulty" IR line set at arch/x86/kernel/apic/apic.c:1349 is  also
0xf6 (specifically APIC IRR for irqs 255 to 224 is 0x400000) which confirms
that something has set the IRQ_WORK_VECTOR line prior to the APIC being
initialized.

Commit 2383844d4850 ("GHES: Elliminate double-loop in the NMI handler")
incorrectly modified the behavior such that the handler returns
NMI_HANDLED only if an error was processed, and incorrectly runs the ghes
work queue for every NMI.

This patch modifies the ghes_proc_irq_work() to run as it did prior to
2383844d4850 ("GHES: Elliminate double-loop in the NMI handler") by
properly returning NMI_HANDLED and only calling the work queue if
NMI_HANDLED has been set.

Fixes: 2383844d4850 (GHES: Elliminate double-loop in the NMI handler)
Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index 0d099a24f776ac9bd665f3aab8006793031aef48..e53bef6cf53c627d7c9a6a566d75fbe1805d1138 100644 (file)
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -852,6 +852,8 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
                if (ghes_read_estatus(ghes, 1)) {
                        ghes_clear_estatus(ghes);
                        continue;
+               } else {
+                       ret = NMI_HANDLED;
                }
 
                sev = ghes_severity(ghes->estatus->error_severity);
@@ -863,12 +865,11 @@ static int ghes_notify_nmi(unsigned int cmd, struct pt_regs *regs)
 
                __process_error(ghes);
                ghes_clear_estatus(ghes);
-
-               ret = NMI_HANDLED;
        }
 
 #ifdef CONFIG_ARCH_HAVE_NMI_SAFE_CMPXCHG
-       irq_work_queue(&ghes_proc_irq_work);
+       if (ret == NMI_HANDLED)
+               irq_work_queue(&ghes_proc_irq_work);
 #endif
        atomic_dec(&ghes_in_nmi);
        return ret;