Re: [PATCH-RESEND] Disable MCE if MCE banks are not present

[Christoph Egger <chegger@amazon.de>]

On 01.06.13 01:04, Andrew Cooper wrote:
> On 31/05/2013 22:46, Aravindh Puthiyaparambil (aravindp) wrote:
>> (My previous email had extra line breaks. Hopefully this one does not. I have also included the patch as an attachement.)

Yep. That's better.

>> Do not continue with machine check setup if MCE banks are not present. This fixes Xen boot on VMware hypervisors.
>>
>> 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>

> 
>>
>> diff --git a/xen/arch/x86/cpu/mcheck/mce.c b/xen/arch/x86/cpu/mcheck/mce.c
>> index 6712db1..9cbd4aa 100644
>> --- a/xen/arch/x86/cpu/mcheck/mce.c
>> +++ b/xen/arch/x86/cpu/mcheck/mce.c
>> @@ -652,7 +652,14 @@ 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%i: 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;
> 
> 
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