8.1-RC2 - PCI fatal error or MCE triggered by USB/ehci on Sun X4100M2?

[Markus Gebert]

On 10.07.2010, at 19:37, Alan Cox wrote:

> On Fri, Jul 9, 2010 at 6:53 PM, Markus Gebert <markus.gebert at hostpoint.ch> wrote:
> [snip]
> 
> Yes, this hardware comes from Sun directly, but getting Sun (/Oracle) support for this issue is gonna be tough. FreeBSD is unsupported, and in a short test we couldn't reproduce the problem with a Linux kernel. While I agree that a hardware issue has always been and still is a possibility to be considered, the fact that we tested this on two machines remains as well as the fact that 6.x, 7.x do not show the behavior. Another possibility is of course, that the X4100 is prone to such issues and somehow 6.x and 7.x have workarounds we're not aware of or just do something different in way so that this issue does not get triggered.
> 
> 
> 8.1 is our first release to have the driver for configuring and reporting machine check exceptions enabled by default.  Prior to 8.1, you had to explicitly enable the driver at boot time.


I was aware of that, but I don't think that it might be the cause. Disabling MCA just makes the reporting go away, but the MCE and subsequent fatal trap remain. With default BIOS settings, the OS does not even get a chance to panic, the system just forces a reset before the OS could do anything. And, as far as I can tell, that did not happen on previous stable branches.

Don't know though wether MCA changes the situation even when disabled in loader.conf (hw.mca.enabled=0). I just checked our 7.2 setup, and MCA does not seem to be in an 7.2 kernel, so I guess this was added to 8.0 and activated by default in 8.1. To be honest, we did not check, wether 8.0 shows the same behavior, but I guess running 8.1 with hw.mca.enabled=0 should pretty much give the same situation as far as MCA is concerned.

Is there a way to get rid of MCA completely? (as opposed to just "turning it off" via loader.conf)


Markus