Re: Dom0 crash with old style AMD NUMA detection

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Sat, Sep 22, 2012 at 01:46:57AM +0200, Andre Przywara wrote:
> On 09/21/2012 07:48 PM, Konrad Rzeszutek Wilk wrote:
> >>Acked-by: Andre Przywara<andre.przywara@amd.com>
> >>
> >>I compiled and boot-tested this on my (single node ;-) test box.
> >>First bare-metal, dmesg: No NUMA configuration found
> >>Then again, but with numa=off on the cmd-line: NUMA turned off
> >>Then under Xen as Dom0 kernel: NUMA turned off
> >>
> >>So the code behaves under Xen as one would have explicitly specified
> >>numa=off, which is what we want.
> >
> >Right.
> >>I couldn't get hold of the test machine (old K8 server) that the bug
> >>was once triggered, that's why I'm reluctant to give my Tested-by.
> >>Will try this ASAP.
> >
> >OK, will wait with this - it would be a bit silly if the patch did not
> >fix the issue :-)
> 
> Thanks for you patience. I tried some machines, it not only affects
> K8s, but also Barcelonas and Magny-Cours.
> Boot those with a Xen HV and restrict Dom0's memory to something
> well below the first node's size (say dom0_mem=512M). If the 3.x
> Dom0 kernel has CONFIG_AMD_NUMA compiled in, the box will crash,
> because the hardware's NUMA info read from the northbridge does not
> fit to Dom0's understanding of it's memory.
> With your fix the box booted fine, NUMA is turned off and everyone is happy.
> Double checked by commenting the numa_off=1 line in your patch:
> crash again. So this line definitely fixes this.
> 
> Tested-by: Andre Przywara <andre.przywara@amd.com>

OK, send out a git pull for it today. If Linus doesn't take it, I will just have
to do it in v3.7 time-frame and do the stable kernel backport.

Thanks again for testing and reporting this!
> 
> Regards,
> Andre.
> 
> -- 
> Andre Przywara
> AMD-Operating System Research Center (OSRC), Dresden, Germany
>