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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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.)
> 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@xxxxxxxxx>

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

>
> 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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