Re: XEN MTRR

[Ben Guthro <ben@guthro.net>]

These were the failures I was seeing:

http://www.nvnews.net/vbulletin/showthread.php?t=174219

going back through old xen-devel emails, the XID failure looks like it
has been happening for about a year, at least.

I have not tried on kernels newer than 3.2

On Thu, Jun 7, 2012 at 7:39 PM, Ben Guthro <ben@guthro.net> wrote:
> On Thu, Jun 7, 2012 at 11:58 AM, Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com> wrote:
>> On Thu, Jun 07, 2012 at 08:49:37PM +1000, aorchis@gmail.com wrote:
>>> On Wed, Jun 6, 2012 at 2:17 AM, Konrad Rzeszutek Wilk
>>> <konrad.wilk@oracle.com> wrote:
>>> > On Sun, Jun 03, 2012 at 05:31:32PM +1000, aorchis@gmail.com wrote:
>>> >> Hi Jeremy and Konrad,
>>> >
>>> > CC-ing xen-devel.
>>> >
>>> >>
>>> >> Basically the driver NVIDIA provided is a binary blob and recent
>>> >> versions does not work with the PAT layout of XEN so it falls back to
>>> >> MTRR to provide write combining (please correct me if I'm wrong).
>>> >
>>> > OK? Which is still OK. Are you using a v3.4 kernel with an up-to-date
>>> > NVidia driver? I've had reports that it works OK.
>>>
>>> I briefly tried kernel 3.4 to see if the problem is fixed but it's not.
>>> I used v3.4 kernel with NVIDIA driver v295.49 and a beta version
>>> (v302) but both didn't work.
>>>
>>> When the nvidia module is loaded, it prints out an error message:
>>> "NVRM: PAT configuration unsupported, falling back to MTRRs."
>>>
>>> When I launch Xorg, the screen turns blank then the monitors powered down and my
>>> box hard crashed, I had to hold the power button to turn it off.
>>
>> Ok, lets CC Ben - he might have more up-to-date information. Also
>> you might want to setup a serial console to capture the kernel to see
>> where it crashes.
>>
>
> Sorry - we ended up needing to abandon using the closed source driver,
> as despite compiling it with IGNORE_XEN_PRESENCE set, I was never able
> to get it to work with the 3.2 linux kernel.
>
> Since we had reasonably good luck with the nouveau drivers, and our
> OpenGL use case is pretty basic - it ended up being sufficient for our
> needs.
>
> I'd have to do some email archeology to see what the specific failure
> was...but it sounds very similar to the problem desribed above.
>
> I apologize that I'm not a lot of help here.
>
> /btg
>
>>>
>>> This only happens in dom0 under XEN, if I run my dom0 by itself then
>>> the nvidia module loads fine.
>>>
>>> >> However there is no MTRR support on XEN so the driver hard crashed my
>>> >> machine (I can't ssh into the box anymore).
>>> >>
>>> >> Moreover, there is problem with the open source driver 'nouveau' for
>>> >> NVIDIA card  (also has something to do with PAT layout of XEN) which
>>> >> causes memory corruption.
>>> >
>>> > Huh? Can you point me to a bugzilla please? There was a corruption
>>> > issue where you can pass in 'nopat' on the command line.
>>>
>>> Yes, that is the issue I was referring to, I had to pass "nopat" to
>>> GRUB in order
>>> to fix it.
>>
>> Ok, so there is afall back for you.