Re: [Xen-devel] XEN MTRR

[Ben Guthro <ben@xxxxxxxxxx>]

On Thu, Jun 7, 2012 at 11:58 AM, Konrad Rzeszutek Wilk
<konrad.wilk@xxxxxxxxxx> wrote:
> On Thu, Jun 07, 2012 at 08:49:37PM +1000, aorchis@xxxxxxxxx wrote:
>> On Wed, Jun 6, 2012 at 2:17 AM, Konrad Rzeszutek Wilk
>> <konrad.wilk@xxxxxxxxxx> wrote:
>> > On Sun, Jun 03, 2012 at 05:31:32PM +1000, aorchis@xxxxxxxxx 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.

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