x86, NMI: Allow NMI reason io port (0x61) to be processed on any CPU
authorDon Zickus <dzickus@redhat.com>
Thu, 6 Jan 2011 21:18:51 +0000 (16:18 -0500)
committerIngo Molnar <mingo@elte.hu>
Fri, 7 Jan 2011 14:08:53 +0000 (15:08 +0100)
In original NMI handler, NMI reason io port (0x61) is only processed
on BSP.  This makes it impossible to hot-remove BSP.  To solve the
issue, a raw spinlock is used to allow the port to be processed on any
CPU.

Originally-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1294348732-15030-6-git-send-email-dzickus@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
arch/x86/kernel/traps.c

index 23f6ac0..613b3d2 100644 (file)
@@ -84,6 +84,11 @@ EXPORT_SYMBOL_GPL(used_vectors);
 static int ignore_nmis;
 
 int unknown_nmi_panic;
+/*
+ * Prevent NMI reason port (0x61) being accessed simultaneously, can
+ * only be used in NMI handler.
+ */
+static DEFINE_RAW_SPINLOCK(nmi_reason_lock);
 
 static inline void conditional_sti(struct pt_regs *regs)
 {
@@ -392,7 +397,6 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 {
        unsigned char reason = 0;
-       int cpu;
 
        /*
         * CPU-specific NMI must be processed before non-CPU-specific
@@ -402,13 +406,12 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
        if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP)
                return;
 
-       cpu = smp_processor_id();
-
-       /* Only the BSP gets external NMIs from the system. */
-       if (!cpu)
-               reason = get_nmi_reason();
+       /* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
+       raw_spin_lock(&nmi_reason_lock);
+       reason = get_nmi_reason();
 
        if (!(reason & NMI_REASON_MASK)) {
+               raw_spin_unlock(&nmi_reason_lock);
                unknown_nmi_error(reason, regs);
 
                return;
@@ -426,6 +429,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
         */
        reassert_nmi();
 #endif
+       raw_spin_unlock(&nmi_reason_lock);
 }
 
 dotraplinkage notrace __kprobes void