From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Egger <chegger@amazon.de>
Subject: Re: [PATCH] Disable MCE if MCE banks are not present
Date: Mon, 3 Jun 2013 11:55:45 +0200
Message-ID: <51AC6821.6070300@amazon.de>
References: <97A500D504438F4ABC02EBA81613CC6322CEA947@xmb-aln-x02.cisco.com>
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To: "Aravindh Puthiyaparambil (aravindp)" <aravindp@cisco.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

On 31.05.13 23:18, Aravindh Puthiyaparambil (aravindp) wrote:
> 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
> <mailto:aravindp@cisco.com>>

Acked-by: Christoph Egger <chegger@amazon.de>

Christoph

> 
>  
> 
> 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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