| From | Kamal Mostafa <> | Subject | [PATCH 3.19.y-ckt 123/160] x86/mce: Ensure offline CPUs don't participate in rendezvous process | Date | Tue, 19 Jan 2016 17:06:41 -0800 |
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3.19.8-ckt13 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Ashok Raj <ashok.raj@intel.com>
commit d90167a941f62860f35eb960e1012aa2d30e7e94 upstream.
Intel's MCA implementation broadcasts MCEs to all CPUs on the node. This poses a problem for offlined CPUs which cannot participate in the rendezvous process:
Kernel panic - not syncing: Timeout: Not all CPUs entered broadcast exception handler Kernel Offset: disabled Rebooting in 100 seconds..
More specifically, Linux does a soft offline of a CPU when writing a 0 to /sys/devices/system/cpu/cpuX/online, which doesn't prevent the #MC exception from being broadcasted to that CPU.
Ensure that offline CPUs don't participate in the MCE rendezvous and clear the RIP valid status bit so that a second MCE won't cause a shutdown.
Without the patch, mce_start() will increment mce_callin and wait for all CPUs. Offlined CPUs should avoid participating in the rendezvous process altogether.
Signed-off-by: Ashok Raj <ashok.raj@intel.com> [ Massage commit message. ] Signed-off-by: Borislav Petkov <bp@suse.de> Reviewed-by: Tony Luck <tony.luck@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: linux-edac <linux-edac@vger.kernel.org> Link: http://lkml.kernel.org/r/1449742346-21470-2-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- arch/x86/kernel/cpu/mcheck/mce.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index 1596e04..c3f58e9 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -1088,6 +1088,17 @@ void do_machine_check(struct pt_regs *regs, long error_code) DECLARE_BITMAP(valid_banks, MAX_NR_BANKS); char *msg = "Unknown"; + /* If this CPU is offline, just bail out. */ + if (cpu_is_offline(smp_processor_id())) { + u64 mcgstatus; + + mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS); + if (mcgstatus & MCG_STATUS_RIPV) { + mce_wrmsrl(MSR_IA32_MCG_STATUS, 0); + return; + } + } + this_cpu_inc(mce_exception_count); if (!cfg->banks) -- 1.9.1
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