Re: [PATCH] nvme: Enable acceleration feature of A64FX processor

From: Keith Busch
Date: Fri Feb 22 2019 - 12:07:16 EST

On Wed, Feb 20, 2019 at 06:46:11PM +0900, Takao Indoh wrote:
> On Thu, Feb 14, 2019 at 08:44:48PM +0000, Elliott, Robert (Persistent Memory) wrote:
> > * how does this interact with an iommu, if there is one? Must the
> > address with bit 56 also be granted permission, or is that
> > stripped off before any iommu comparisons?
> The latter. A bit 56 is cleared in Root Port before pass it to iommu.

What if the intendend destination is a peer and never hits the root port?

Really, though, PCI device vendors need to just use the existing
capability as intended and not have arch specific work-arounds. I'm sure
nvme can't be the only device class you'd want this behavior.