x86/MCE: disable if MCE banks are not present

When booting Xen on VMware ESX 5.1 and Workstation 9, you hit a GPF
during MCE initialization. The culprit is line 631 in
set_poll_bankmask():
                bitmap_copy(mb->bank_map, mca_allbanks->bank_map, nr_mce_banks);

What is happening is that in mca_cap_init(), nr_mce_banks is being set
to 0. This causes the allocation of bank_map to be set to
ZERO_BLOCK_PTR which is the return value for zero-size allocation by
xzalloc_array()/_xmalloc(). This results in the bitmap_copy() to fail
disastrously. The following patch fixes this issue.

Signed-off-by: Aravindh Puthiyaparambil <aravindp@cisco.com>
Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Acked-by: Christoph Egger <chegger@amazon.de>
master commit: 5cffb77c4072fa5b46700a2dbb3e46c5a54eba6d
master date: 2013-06-03 15:42:46 +0200

1 files changed, 8 insertions, 1 deletions

diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
index 50596e3db5..d03769c3e0 100644
--- a/xen/arch/x86/cpu/mcheck/mce.c
+++ b/xen/arch/x86/cpu/mcheck/mce.c
@@ -739,7 +739,14 @@ int mca_cap_init(void)
     }
     nr_mce_banks = msr_content & MCG_CAP_COUNT;
 
-    /* mcabanks_alloc depends on nr_mcebanks */
+    if (!nr_mce_banks)
+    {
+        printk(XENLOG_INFO "CPU%u: No MCE banks present. "
+               "Machine check support disabled\n", smp_processor_id());
+        return -ENODEV;
+    }
+
+    /* mcabanks_alloc depends on nr_mce_banks */
     if (!mca_allbanks)
     {
         int i;