x86/mce: Ensure offline CPUs don't participate in rendezvous process

Orabug: 23520972

mainline commit d90167a941f62860f35eb960e1012aa2d30e7e94

Conflicts:
    The following changes are done to resolve the conflict.

    - ist_enter(regs);
    + prev_state = ist_enter(regs);

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: <stable@vger.kernel.org>
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: Ashok Vairavan <ashok.vairavan@oracle.com>

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 20190bdac9d58ecabddd3cbe6692d0f52bb687ad..bb3839f1a10fdac0e5fe369dade36b5526aebcdd 100644 (file)
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -1051,6 +1051,17 @@ void do_machine_check(struct pt_regs *regs, long error_code)
        u64 recover_paddr = ~0ull;
        int flags = MF_ACTION_REQUIRED;
 
+       /* 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;
+               }
+       }
+
        prev_state = ist_enter(regs);
 
        this_cpu_inc(mce_exception_count);