Re: [Xen-devel] Re: [PATCH] infiniband/mthca : Fix userland mapping of mthca infiniband cards in Xen dom0

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Thu, Jan 06, 2011 at 10:51:57AM -0800, Roland Dreier wrote:
>  > There is another way, which I hope can fix this issue (it fixes
>  > the graphics drivers). Basically making the Xen MMU be aware of the E820
>  > and consider any access to PFNs that are not in RAM to have VM_IO 
> implicitly set.
>  > 
>  > The patches are at 
> git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git
>  > 
>  > stable/p2m-identity.v4.3
>  > 
>  > And posted on LKML )https://lkml.org/lkml/2010/12/30/163)
>  > 
>  > They _should_ take care of your problem as long as the PFNs you
>  > are mapping fall within the PCI BAR regions (which I would presume they
>  > do since you are using ioremap).
> 
> Yes, that should work fine for all the cases I know of in the RDMA
> drivers.  We are just mapping some PCI BAR space into userspace for
> direct access to hardware (just like graphics, I think).

Allright, then it will work. 

I've respun another version that fundamentally does the same thing
but accounts for  "what PFN is non-RAM" in a much cleaner way.

It is @:

git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git 
devel/p2m-identity.v4.5

will post it soon on LKML.

Jack, Vivien: i you do merge it in your tree for testing with Xen and it works 
properly can
I attach your 'Tested-by' on the patch-set?

> 
> I definitely prefer a solution that doesn't require driver authors to
> add a Xen-specific fix that isn't required on any other architecture.

Heh. You and me are on the same wavelength here.

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