On Tue, Oct 06, 2026 at 04:08:48PM -0500, Bjorn Helgaas wrote: > On Thu, Oct 01, 2026 at 02:55:12PM +0300, Leon Romanovsky wrote: > > From: Leon Romanovsky <[email protected]> > > > > ACS redirect controls choose between peer and upstream routes only at the > > path divergence. Applying them below that point rejects valid nested > > topologies because traffic already has only an upstream route. > > I guess the point here is that prior to this patch, > calc_map_type_and_dist() returned PCI_P2PDMA_MAP_NOT_SUPPORTED in a > case where it didn't need to? Can you include an example to make this > concrete?
One possible example I had in mind while preparing the presentation [1] was ability to connect devices to different switches. Despite devices and switches support P2P, but from the P2P subsystem's point of view, traffic between them was not P2P (see slide 4). This support will become even more important when we reach the point of enabling P2P inside a VM. It will allow us to hide the underlying PCI topology from the VM. Thanks [1] http://lpc.events/event/20/contributions/2508/
