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Re: [Xen-devel] RE: How to generate a HW NMI

To: "Jan Kiszka" <jan.kiszka@xxxxxxxxxxx>
Subject: Re: [Xen-devel] RE: How to generate a HW NMI
From: "Roger Cruz" <roger.cruz@xxxxxxxxxxxxxxxxxxx>
Date: Tue, 12 Oct 2010 08:42:13 -0400
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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Thread-topic: [Xen-devel] RE: How to generate a HW NMI
Disabling SMIs is part of the experiments to be conducted today or tomorrow. I will keep u posted.

On Oct 12, 2010, at 4:48 AM, "Jan Kiszka" <jan.kiszka@xxxxxxxxxxx> wrote:

Am 11.10.2010 23:20, Roger Cruz wrote:
Here is some additional info from my experiments over the weekend.

I took the Lenovo T500 and removed its internal WiFi miniPCIe card. In
its place, I put in a miniPCIe to PCIe converter card with a PCIe
socket. Into that socket, I placed a PCIe dump card. This card has a
switch that when you press it, it creates an SERR error.  Using the
utility provided by the vendor, I enabled all the bridges between the
card to carry the SERR signal to the CPU and cause the CPU to see it as an NMI. I tested the set-up several times. Every single time I pressed the switch, I got an NMI, followed by a kdump core. So I was sure the
HW setup was working correctly.

I left two Lenovo T500 running over the weekend and when I returned this morning, both had hung. Completely frozen. I pressed the NMI switch in both systems and nothing. No crashes, no coredumps. It looks as if the
SERR/NMI is getting ignored/blocked or CPU is completely shutdown

This experiment helps me prove that the software watchdog code in Xen
was not the problem and indeed the NMIs are getting blocked somehow.
This is what I now need to investigate. Areas that I care to learn more
about are the SMI handler and the external chip's use of the STPCLK
signal to the CPU.

As an additional bit of info, the only response we get when the systems
are hung is a beep when the power cord is unplugged/plugged from the
laptop.  I don't know if the beep is done via a HW module or whether
ACPI/BIOS is involved.

Still looking for additional ideas.

Already tried to disable SMIs?


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