Implement simple machine check support for amd64 and i386.

- For CPUs that only support MCE (the machine check exception) but not MCA
  (i.e. Pentium), all this does is print out the value of the machine check
  registers and then panic when a machine check exception occurs.
- For CPUs that support MCA (the machine check architecture), the support is
  a bit more involved.
  - First, there is limited support for decoding the CPU-independent MCA
    error codes in the kernel, and the kernel uses this to output a short
    description of any machine check events that occur.
  - When a machine check exception occurs, all of the MCx banks on the
    current CPU are scanned and any events are reported to the console
    before panic'ing.
  - To catch events for correctable errors, a periodic timer kicks off a
    task which scans the MCx banks on all CPUs.  The frequency of these
    checks is controlled via the "hw.mca.interval" sysctl.
  - Userland can request an immediate scan of the MCx banks by writing
    a non-zero value to "hw.mca.force_scan".
  - If any correctable events are encountered, the appropriate details
    are stored in a 'struct mca_record' (defined in <machine/mca.h>).
    The "hw.mca.count" is a count of such records and each record may
    be queried via the "hw.mca.records" tree by specifying the record
    index (0 .. count - 1) as the next name in the MIB similar to using
    PIDs with the kern.proc.* sysctls.  The idea is to export machine
    check events to userland for more detailed processing.
  - The periodic timer and hw.mca sysctls are only present if the CPU
    supports MCA.

Discussed with:	emaste (briefly)
MFC after:	1 month

1 files changed, 3 insertions, 0 deletions

diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index 7a93023..f398a24 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -60,6 +60,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/clock.h>
 #include <machine/cputypes.h>
 #include <machine/cpufunc.h>
+#include <machine/mca.h>
 #include <machine/md_var.h>
 #include <machine/mp_watchdog.h>
 #include <machine/pcb.h>
@@ -667,6 +668,8 @@ init_secondary(void)
 	KASSERT(PCPU_GET(idlethread) != NULL, ("no idle thread"));
 	PCPU_SET(curthread, PCPU_GET(idlethread));
 
+	mca_init();
+
 	mtx_lock_spin(&ap_boot_mtx);
 
 	/* Init local apic for irq's */