Re: [PATCH v9 00/18] PCI/P2PDMA: Route peer-to-peer DMA by TLP class

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Oct 01, 2026 at 02:55:08PM +0300, Leon Romanovsky wrote:
> PCI P2PDMA applies Request and Completion Redirect throughout both paths.
> This misclassifies asymmetric and nested switches, and reports one answer
> for every kind of TLP.
> 
> Three ACS controls act on TLP attributes the client chooses rather than
> on the topology: Translation Blocking and Direct Translated P2P act on
> a Request's Address Type, and Completion Redirect skips Completions carrying
> Relaxed Ordering.
> 
> Evaluate each direction at the path divergence, decide every class from the
> one walk, and treat a client with ATS enabled as translating unless its
> driver declares per-mapping ATS.
> 
> This completes the P2PDMA side; dma-buf and mlx5 follow separately.
> ...

> Leon Romanovsky (18):
>       PCI/P2PDMA: Document the TLP attribute assumptions
>       PCI/P2PDMA: Derive routing from directional ACS controls
>       PCI: Reject unreadable ACS controls in isolation checks
>       PCI/P2PDMA: Evaluate ACS controls at the path divergence
>       PCI/P2PDMA: Document directional ACS routing
>       PCI/P2PDMA: Collect the path's ACS controls before deciding
>       PCI/P2PDMA: Answer routing per TLP class
>       PCI/P2PDMA: Route Relaxed Ordering Completions directly
>       PCI/P2PDMA: Reject Translated Requests blocked by Translation Blocking
>       PCI/P2PDMA: Route Translated Requests under Direct Translated P2P
>       PCI/P2PDMA: Log detailed ACS routing diagnostics
>       PCI/P2PDMA: Add KUnit tests for the ACS routing decisions
>       PCI/P2PDMA: Test the ACS P2P routing walk
>       PCI: Add KUnit coverage for ACS isolation checks
>       PCI/P2PDMA: Document TLP-class routing
>       PCI/P2PDMA: Let a client declare that it selects ATS per mapping
>       PCI/P2PDMA: Evaluate the ATS path for clients with ATS enabled
>       PCI/P2PDMA: Test the routing of clients with ATS enabled
> 
>  Documentation/admin-guide/kernel-parameters.txt |  15 +-
>  Documentation/driver-api/pci/p2pdma.rst         |  80 +++
>  drivers/pci/Kconfig                             |  15 +
>  drivers/pci/Makefile                            |   1 +
>  drivers/pci/p2pdma.c                            | 719 ++++++++++++++++++--
>  drivers/pci/pci.c                               |   7 +-
>  drivers/pci/pci.h                               |  58 ++
>  drivers/pci/pci_acs_test.c                      | 860 ++++++++++++++++++++++++
>  drivers/pci/quirks.c                            |   6 +-
>  include/linux/pci-p2pdma.h                      |  12 +-
>  10 files changed, 1687 insertions(+), 86 deletions(-)
> ---
> base-commit: 08dbfad3f5040f5bdb6c529da20d6d4e81fefd72
> change-id: 20260821-fix-p2p-acs-v4-0-e72455e3a261
> prerequisite-message-id: <20260830-batch-p2p-fixes-v1-0-5044e8dfbe2e@nvidia.com>
> prerequisite-patch-id: 6b25c7fcf164cdfc14e9fac5b908d97fcf6509d7
> prerequisite-patch-id: 0d083c281001365aae4b35544cf28891a6ab9a96
> prerequisite-patch-id: bfd9dabf271f3cc9a3a61f46387d20c20311363d
> prerequisite-patch-id: fad0275efc722830fc591509506c0a5e4f581073
> prerequisite-patch-id: 0c83bee688fec1f6d1564654df7c630fa6a4a978

This seems like material for the PCI tree, but I'm not sure how to
apply it.  It doesn't apply cleanly on the current pci/p2pdma
(https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/log/?h=p2pdma),
which does contain your series from
20260830-batch-p2p-fixes-v1-0-5044e8dfbe2e@nvidia.com.

I could probably fix the conflicts but I don't know why there should
be conflicts, since the only commits on pci/p2pdma other than yours
are a few trivial allow-list updates.

Bjorn