From: Jason Gunthorpe <jgg@ziepe.ca>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: "Leon Romanovsky" <leon@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Logan Gunthorpe" <logang@deltatee.com>,
"Joerg Roedel (AMD)" <joro@8bytes.org>,
"Will Deacon" <will@kernel.org>,
"Robin Murphy" <robin.murphy@arm.com>,
"Christian König" <christian.koenig@amd.com>,
"Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, iommu@lists.linux.dev,
"Tushar Dave" <tdave@nvidia.com>,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linaro-mm-sig@lists.linaro.org, linux-rdma@vger.kernel.org,
kvm@vger.kernel.org, "Chaitanya Kulkarni" <kch@nvidia.com>,
"Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
"Jens Axboe" <axboe@kernel.dk>,
"Alex Williamson" <alex@shazbot.org>,
"Ankit Agrawal" <ankita@nvidia.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <skhan@linuxfoundation.org>,
"Randy Dunlap" <rdunlap@infradead.org>,
"Sumit Semwal" <sumit.semwal@linaro.org>
Subject: Re: [PATCH v9 02/18] PCI/P2PDMA: Derive routing from directional ACS controls
Date: Fri, 23 Oct 2026 16:00:36 -0300 [thread overview]
Message-ID: <20261023190036.GL3977851@ziepe.ca> (raw)
In-Reply-To: <20261023182715.GA2798722@bhelgaas>
On Fri, Oct 23, 2026 at 01:27:15PM -0500, Bjorn Helgaas wrote:
> > Yes, the ACS combination is selected to avoid ordering issues
>
> Does a user have any way to know whether the configuration is safe?
No, unfortunately in PCIe so much is really difficult when it comes to
deployment :(
> I'm wondering whether users might use "pci=config_acs=" to configure
> ACS so things appear to work as they prefer but may not provide the
> ordering guarantees drivers depend on.
I imagine that could happen, but on most practical systems the root
complex will blow up if you do asymmetric routing so there is an early
indication.
I know this because I've help debug such configurations at
customers. Some servers helpfully MCE if you do this. Lovely.
> If that's a possibility, do we have any notes in dmesg that we are
> depending on fabric behavior that the OS can't discover and verify?
Maybe, it could be interesting if the P2P logic found asymetric paths
it refuses to permit it.
Jason
next prev parent reply other threads:[~2026-10-23 19:00 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-01 11:55 [PATCH v9 00/18] PCI/P2PDMA: Route peer-to-peer DMA by TLP class Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 01/18] PCI/P2PDMA: Document the TLP attribute assumptions Leon Romanovsky
2026-10-07 20:12 ` Bjorn Helgaas
2026-10-12 11:02 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 02/18] PCI/P2PDMA: Derive routing from directional ACS controls Leon Romanovsky
2026-10-06 20:49 ` Bjorn Helgaas
2026-10-07 6:32 ` Leon Romanovsky
2026-10-07 20:40 ` Bjorn Helgaas
2026-10-09 17:43 ` Leon Romanovsky
2026-10-23 15:59 ` Jason Gunthorpe
2026-10-23 18:27 ` Bjorn Helgaas
2026-10-23 19:00 ` Jason Gunthorpe [this message]
2026-10-23 20:15 ` Bjorn Helgaas
2026-10-23 22:01 ` Jason Gunthorpe
2026-10-01 11:55 ` [PATCH v9 03/18] PCI: Reject unreadable ACS controls in isolation checks Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 04/18] PCI/P2PDMA: Evaluate ACS controls at the path divergence Leon Romanovsky
2026-10-06 21:08 ` Bjorn Helgaas
2026-10-07 10:51 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 05/18] PCI/P2PDMA: Document directional ACS routing Leon Romanovsky
2026-10-06 21:32 ` Bjorn Helgaas
2026-10-07 13:46 ` Leon Romanovsky
2026-10-07 20:10 ` Bjorn Helgaas
2026-10-01 11:55 ` [PATCH v9 06/18] PCI/P2PDMA: Collect the path's ACS controls before deciding Leon Romanovsky
2026-10-06 21:48 ` Bjorn Helgaas
2026-10-07 13:50 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 07/18] PCI/P2PDMA: Answer routing per TLP class Leon Romanovsky
2026-10-09 21:25 ` Bjorn Helgaas
2026-10-12 11:57 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 08/18] PCI/P2PDMA: Route Relaxed Ordering Completions directly Leon Romanovsky
2026-10-06 22:21 ` Bjorn Helgaas
2026-10-12 10:57 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 09/18] PCI/P2PDMA: Reject Translated Requests blocked by Translation Blocking Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 10/18] PCI/P2PDMA: Route Translated Requests under Direct Translated P2P Leon Romanovsky
2026-10-06 22:28 ` Bjorn Helgaas
2026-10-12 11:53 ` Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 11/18] PCI/P2PDMA: Log detailed ACS routing diagnostics Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 12/18] PCI/P2PDMA: Add KUnit tests for the ACS routing decisions Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 13/18] PCI/P2PDMA: Test the ACS P2P routing walk Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 14/18] PCI: Add KUnit coverage for ACS isolation checks Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 15/18] PCI/P2PDMA: Document TLP-class routing Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 16/18] PCI/P2PDMA: Let a client declare that it selects ATS per mapping Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 17/18] PCI/P2PDMA: Evaluate the ATS path for clients with ATS enabled Leon Romanovsky
2026-10-01 11:55 ` [PATCH v9 18/18] PCI/P2PDMA: Test the routing of " Leon Romanovsky
2026-10-06 19:29 ` [PATCH v9 00/18] PCI/P2PDMA: Route peer-to-peer DMA by TLP class Bjorn Helgaas
2026-10-06 21:22 ` Leon Romanovsky
2026-10-06 21:36 ` Bjorn Helgaas
2026-10-07 6:56 ` Bjorn Helgaas
2026-10-07 10:54 ` Leon Romanovsky
2026-10-07 11:31 ` Bjorn Helgaas
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20261023190036.GL3977851@ziepe.ca \
--to=jgg@ziepe.ca \
--cc=alex@shazbot.org \
--cc=ankita@nvidia.com \
--cc=axboe@kernel.dk \
--cc=bhelgaas@google.com \
--cc=christian.koenig@amd.com \
--cc=corbet@lwn.net \
--cc=dri-devel@lists.freedesktop.org \
--cc=gregkh@linuxfoundation.org \
--cc=helgaas@kernel.org \
--cc=iommu@lists.linux.dev \
--cc=joro@8bytes.org \
--cc=kch@nvidia.com \
--cc=kvm@vger.kernel.org \
--cc=leon@kernel.org \
--cc=linaro-mm-sig@lists.linaro.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-media@vger.kernel.org \
--cc=linux-pci@vger.kernel.org \
--cc=linux-rdma@vger.kernel.org \
--cc=logang@deltatee.com \
--cc=rdunlap@infradead.org \
--cc=robin.murphy@arm.com \
--cc=skhan@linuxfoundation.org \
--cc=sumit.semwal@linaro.org \
--cc=tdave@nvidia.com \
--cc=thomas.hellstrom@linux.intel.com \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®