Re: [PATCH] xen: Don't call arch_trigger_all_cpu_backtrace in dom0(pvm)

[Zhenzhong Duan <zhenzhong.duan@oracle.com>]

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@x4470m2-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@x4470m2-bur09-b ~]# cat /proc/cpuinfo | grep x2apic
[root@x4470m2-bur09-b ~]# dmesg | grep x2apic
[root@x4470m2-bur09-b ~]# cat /proc/cmdline
ro root=UUID=486fc42b-3383-462f-aca3-b1340fbd4ad9 console=tty1 console=ttyS0,9600n8
[root@x4470m2-bur09-b ~]# echo l > /proc/sysrq-trigger
[root@x4470m2-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.