On 10/06/2015 at 12:13 PM, Joerg Roedel wrote:
> On Wed, Sep 30, 2015 at 04:52:47PM +0200, Andreas Hartmann wrote:
>>> Alternativly someone who can reproduce it should trace the calls to
>>> __map_single and __unmap_single in the AMD IOMMU driver to find out
>>> whether the addresses which the faults happen on are really mapped, or
>>> at least requested from the AMD IOMMU driver.
>>
>> How can I trace it?
> 
> Please apply the attached debug patch on-top of Linux v4.3-rc3 and boot
> the machine. After boot you run (as root):
> 
> 
> 	# cat /sys/kernel/debug/tracing/trace_pipe > trace-data
> 
> Please run this in a seperate shell an keep it running.
> 
> Then trigger the problem while the above command is running. When you
> triggered it, please send me the (compressed) trace-data file, full
> dmesg and output of lspci on the box.

Hmm, *seems* to work fine w/ 4.3-rc2. But I have to do some more tests
to be really sure.


W/ 4.1.10, the problem can be seen most always during boot (systemd) -
but at this point, it is difficult to trace. I have to take a closer
look to find a place to start the trace already during boot process.


But there is another problem w/ 4.3-rc2: Starting a VM w/ PCIe
passthrough doesn't work any more. I'm getting the attached null pointer
dereference and the machine hangs.


Thanks,
regards,
Andreas