linux-kernel - Re: [PATCH] xen: Don't call arch_trigger_all_cpu

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Date:	Wed, 3 Apr 2013 10:46:00 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Feng Jin <joe.jin@...cle.com>,
	Tamon Shiose <tamon.shiose@...cle.com>
Subject: Re: [PATCH] xen: Don't call arch_trigger_all_cpu_backtrace in
 dom0(pvm)

On Wed, Apr 03, 2013 at 08:00:37PM +0800, Zhenzhong Duan wrote:
> 
> On 2013-04-01 20:41, Konrad Rzeszutek Wilk wrote:
> >On Mon, Apr 01, 2013 at 01:26:34PM +0800, Zhenzhong Duan wrote:
> >>On 2013-03-29 21:46, Konrad Rzeszutek Wilk wrote:
> >>>On Fri, Mar 29, 2013 at 03:22:38PM +0800, Zhenzhong Duan wrote:
> >>The problem is even without overwrite, like xapic system,
> >>xen_send_IPI_all doesn't work for nmi vector.
> >Can you tweak the x2apic_mode = 0 in enligthen.c for example?
> >Or clear the X86_FEATURE_X2APIC in the enlighten.c ? (Similar
> >to how the other features are cleared) Wouldn't
> >that stop x2apic_enabled from detecting x2APIC?
> Hi Konrad,
> I used the second method. x2apic is totally masked in dom0. Thanks
> Tamon to do the test.
> 
> Testing result:
> 
> The server didn't get crashed by "echo l > /proc/sysrq-trigger". On this machine, VT-d is enabled in BIOS.
> However, no backtrace was shown.
> 
> [root@...70m2-bur09-b ~]# uname -a
> Linux x4470m2-bur09-b.us.oracle.com 2.6.39-200.1.14.el5uek.bug16372098.test #1 SMP Tue Apr 2 21:09:27 PDT 2013 x86_64 x86_64 x86_64 GNU/Linux
> [root@...70m2-bur09-b ~]# cat /proc/cpuinfo | grep x2apic
> [root@...70m2-bur09-b ~]# dmesg | grep x2apic
> [root@...70m2-bur09-b ~]# cat /proc/cmdline
> ro root=UUID=486fc42b-3383-462f-aca3-b1340fbd4ad9 console=tty1 console=ttyS0,9600n8
> [root@...70m2-bur09-b ~]# echo l > /proc/sysrq-trigger
> [root@...70m2-bur09-b ~]#
> 
> /var/log/messages:
> (snip)
> Apr  3 14:14:33 x4470m2-bur09-b kernel: SysRq : Show backtrace of all active CPUs
> Apr  3 14:14:33 x4470m2-bur09-b kernel: sending NMI to all CPUs:
> (EOF)
> 
> On the console, no backtrace either. I did it twice, and got the same results.

Great.
Zhenzhong, do you want to prep a patch with a nice git commit description mentioning
your findings of the x2APIC over-write and also include the crach that would
appear?

And send it to xen-devel + LKML and to me so I can put it on my v3.9 branch?

Thanks
> 
> 
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