Re: [PATCH v2] ACPI / APEI: Fix NMI notification handling

[Borislav Petkov]

On Wed, Nov 30, 2016 at 08:19:39AM -0500, Prarit Bhargava wrote:
> 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.
> 
> v2: Borislav, setting of NMI_HANDLED moved & cleaned up changelog.
> 
> Fixes: 2383844d4850 ("GHES: Elliminate double-loop in the NMI handler")
> Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
> Cc: Borislav Petkov <bp@xxxxxxx>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Cc: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
> Cc: Tyler Baicar <tbaicar@xxxxxxxxxxxxxx>
> Cc: Punit Agrawal <punit.agrawal@xxxxxxx>
> Cc: Don Zickus <dzickus@xxxxxxxxxx>
> ---
>  drivers/acpi/apei/ghes.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Reviewed-by: Borislav Petkov <bp@xxxxxxx>

-- 
Regards/Gruss,
    Boris.

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