[Xen-users] Xen, PAT and MTRR (Was Re: Xen and nvidia)

[Howell Tam <pigeon@xxxxxxxxxxx>]

Hi,

> Try adding nopat as a cmdline argument to your dom0 kernel.
> 
> here's my grub entries as an example.
> 
> kernel /xen-4.1.4.gz dom0_mem=2048M dom0_max_vcpus=2 dom0_vcpus_pin
> module /lfskernel-3.7.1 ro root=/dev/md0 nopat


        Thanks.

        I ended up going back to trying Xen 4.2 and I can get the nvidia 
drivers to work in Dom0, even without nopat, but with very bad 3d performance. 
And sometimes it still get the Xorg 100% cpu problem, and I can see
the nvidia driver printing out a few Xid messages.


    After a bit of research i realized i'm hitting the PAT problem, which has 
been mentioned for quite a while. This affects all display cards, not just 
nvidia it seems. 


   From what i understand now, PAT has been disabled now in the kernel by 
Konrad:

http://lists.xen.org/archives/html/xen-devel/2012-02/msg01634.html

    which he had an attempt to fix the underlying problem:

https://lkml.org/lkml/2012/2/10/228


    Looking at the latest stable 3.7.2 kernel, PAT is still disabled in xen.


    Does anyone know the status of this? (Should I ask on xen-devel or Konrad?)


    And while I'm at this, what about the MTRR support in Xen?


    Thanks.


Regards,
Howell.

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