# HG changeset patch
# Parent ac68ad6fe4b779ca0b894ca3845b66662dd2dd9c
CMCI: Fix pagefault

The CMCI handler blindly dereferences the dom0 pointer.  If a CMCI occurs during
early boot, this results in a page fault and reboot.

Check the dom0 pointer first.  If it is null, then the CMCI information is
dumped onto the Xen console, and booting continues happily.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

diff -r ac68ad6fe4b7 xen/arch/x86/cpu/mcheck/mce_intel.c
--- a/xen/arch/x86/cpu/mcheck/mce_intel.c
+++ b/xen/arch/x86/cpu/mcheck/mce_intel.c
@@ -705,7 +705,7 @@ fastcall void smp_cmci_interrupt(struct 
         MCA_CMCI_HANDLER, __get_cpu_var(mce_banks_owned), &bs);
 
     if (bs.errcnt && mctc != NULL) {
-        if (guest_enabled_event(dom0->vcpu[0], VIRQ_MCA)) {
+        if (dom0 && guest_enabled_event(dom0->vcpu[0], VIRQ_MCA)) {
             mctelem_commit(mctc);
             printk(KERN_DEBUG "CMCI: send CMCI to DOM0 through virq\n");
             send_guest_global_virq(dom0, VIRQ_MCA);