[dpdk-dev] [PATCH] eal: add option to force IOVA as PA mode

[Chas Williams]

Thanks, and yes I already saw that.  That seems like a much better
solution.  I will give it a spin in my box with this problem.

On Thu, Jan 11, 2018 at 7:12 PM, Thomas Monjalon <thomas at monjalon.net>
wrote:

> 03/12/2017 01:23, Chas Williams:
> > The particular machine in my case is a Dell Optiplex 790 which is fairly
> > similar to another system that has basically the same problem.  The IOMMU
> > advertises that is can only handle 39 bits of addressing.  The DMAR
> address
> > tables have a width of 36 bits, so all is well when using IOVA physical
> > addresses.  With IOVA virtual addresses, they sometimes go beyond the 39
> > bit boundary.  I was under the impression that IOMMU widths are more
> > typically 48 bits, but I appear to have some low end systems with a
> simpler
> > IOMMU.
> >
> > I could make it a runtime option.
> >
> > On Thu, Nov 30, 2017 at 4:17 AM, Thomas Monjalon <thomas at monjalon.net>
> > wrote:
> >
> > > 30/11/2017 03:57, Chas Williams:
> > > > From: Chas Williams <chas3 at att.com>
> > > >
> > > > The IOMMU in some machines report that they can only support
> > > > limited widths.  IOVA virtual addresses may exceed this width
> > > > making the use of IOVA virtual addresses difficult.  The option
> > > > CONFIG_RTE_LIBRTE_USE_PHYS_IOVA can used to force IOVA physical
> > > > address usage.
> > >
> > > Which machines are you talking about?
> > > A run-time option may be a better solution.
>
> Please check the patch from Maxime:
>         https://dpdk.org/dev/patchwork/patch/33192/
>
>
>