From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH-RESEND] Disable MCE if MCE banks are not present Date: Sat, 1 Jun 2013 00:04:29 +0100 Message-ID: <51A92C7D.20600@citrix.com> References: <97A500D504438F4ABC02EBA81613CC6322CEAA55@xmb-aln-x02.cisco.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <97A500D504438F4ABC02EBA81613CC6322CEAA55@xmb-aln-x02.cisco.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: "Aravindh Puthiyaparambil (aravindp)" Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org 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 Reviewed-by: Andrew Cooper > > 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;