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* [Patch V2] x86, mce: Ensure offline CPU's don't participate in mce rendezvous process.
@ 2015-12-05  0:29 Ashok Raj
  2015-12-07 20:00 ` Borislav Petkov
  0 siblings, 1 reply; 13+ messages in thread
From: Ashok Raj @ 2015-12-05  0:29 UTC (permalink / raw)
  To: linux-kernel; +Cc: Boris Petkov, linux-edac, Tony Luck, Ashok Raj

Linux has logical cpu offline capability. That can be triggered by:

# echo 0 > /sys/devices/system/cpu/cpuX/online

In Intel Architecture, MCE's are broadcasted to all CPUs in the system.

This includes the CPUs marked offline by Linux. Unless the CPU's were removed
via an ACPI notification, in which case the cpu's are removed from the
cpu_present_map.

This patch ensures offline CPU's don't participate in MCE rendezvous, but
simply perform clearing some status bits to ensure a second MCE wont cause
automatic shutdown.

Without the patch, mce_start will increment mce_callin, but mce_start would
only wait for all online_cpus. So offline cpu's should avoid participating
in the rendezvous process.

Reviewed-by: Tony Luck <tony.luck@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ashok Raj <ashok.raj@intel.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index c5b0d56..23ecb1d 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -998,7 +998,20 @@ void do_machine_check(struct pt_regs *regs, long error_code)
 	u64 recover_paddr = ~0ull;
 	int flags = MF_ACTION_REQUIRED;
 	int lmce = 0;
+	unsigned int cpu = smp_processor_id();
+
+	/*
+	 * if this cpu is offline, just bail out.
+	 */
+	if (cpu_is_offline(cpu)) {
+		u64 mcgstatus;
 
+		mcgstatus = mce_rdmsrl(MSR_IA32_MCG_STATUS);
+		if (mcgstatus & MCG_STATUS_RIPV) {
+			mce_wrmsrl(MSR_IA32_MCG_STATUS, 0);
+			return;
+		}
+	}
 	ist_enter(regs);
 
 	this_cpu_inc(mce_exception_count);
-- 
2.4.3


^ permalink raw reply related	[flat|nested] 13+ messages in thread

end of thread, other threads:[~2015-12-08 18:57 UTC | newest]

Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-12-05  0:29 [Patch V2] x86, mce: Ensure offline CPU's don't participate in mce rendezvous process Ashok Raj
2015-12-07 20:00 ` Borislav Petkov
2015-12-07 20:04   ` Luck, Tony
2015-12-07 20:19     ` Borislav Petkov
2015-12-07 22:07       ` Luck, Tony
2015-12-07 22:34         ` Borislav Petkov
2015-12-07 23:26           ` Luck, Tony
2015-12-07 23:46           ` Raj, Ashok
2015-12-07 23:25             ` Borislav Petkov
2015-12-08  1:41               ` Raj, Ashok
2015-12-08  9:18                 ` Borislav Petkov
2015-12-08 15:59                   ` Luck, Tony
2015-12-08 18:56                     ` Borislav Petkov

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