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

[Thomas Monjalon <thomas@monjalon.net>]

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@monjalon.net>
> wrote:
> 
> > 30/11/2017 03:57, Chas Williams:
> > > From: Chas Williams <chas3@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/