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From: "Thomas Hellström" <thomas.hellstrom@linux.intel.com>
To: "Christian König" <christian.koenig@amd.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Christoph Hellwig" <hch@lst.de>
Cc: Leon Romanovsky <leon@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	 Logan Gunthorpe <logang@deltatee.com>,
	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>,
	"Joerg Roedel (AMD)"	 <joro@8bytes.org>,
	Will Deacon <will@kernel.org>,
	Robin Murphy	 <robin.murphy@arm.com>,
	Randy Dunlap <rdunlap@infradead.org>,
	Sumit Semwal	 <sumit.semwal@linaro.org>,
	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
Subject: Re: [PATCH v6 18/18] RDMA/mlx5: Ask P2PDMA whether ATS takes a direct peer-to-peer route
Date: Mon, 21 Sep 2026 08:57:31 +0200	[thread overview]
Message-ID: <e80dc629b90d5284ace6f84643616f352f25cb57.camel@linux.intel.com> (raw)
In-Reply-To: <9656f2f9-2e39-4007-b065-3b763b53c6de@amd.com>

On Mon, 2026-09-21 at 08:43 +0200, Christian König wrote:
> On 9/18/26 19:05, Jason Gunthorpe wrote:
> > On Fri, Sep 18, 2026 at 03:42:28PM +0200, Thomas Hellström wrote:
> > > 
> > > 1) Xe attachment check if pci_p2pdma_distance() returns OK for
> > > the
> > > path. Then Xe always sets up dma-addresses using
> > > dma_map_resource(). 
> > 
> > Open coding pci_p2pdma_distance() in drivers is a hack. Using
> > dma_map_resource() like this was never "allowed".
> > 
> > We've fixed things so these hacks are not needed, the drivers need
> > to
> > move over to things like dma_buf_phys_vec_to_sgt() and the hmm
> > helpers
> > to use the DMA API correctly.
> 
> That is a completely broken approach as well since it limits the
> exported resources to addresses the CPU can reach.

And this would be OK for pcie_p2p, but not for other fast
interconnects, right? Or is this problematic also for pcie_p2p?

Thanks,
Thomas

  reply	other threads:[~2026-09-21  6:57 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-09-14 11:22 [PATCH v6 00/18] PCI/P2PDMA: Route peer-to-peer DMA by TLP class Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 01/18] PCI/P2PDMA: Document pdev->p2pdma lifetime rules Leon Romanovsky
2026-09-18 18:25   ` Logan Gunthorpe
2026-09-19  4:39     ` Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 02/18] PCI/P2PDMA: Document the TLP attribute assumptions Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 03/18] PCI/P2PDMA: Derive routing from directional ACS controls Leon Romanovsky
2026-09-18 19:39   ` Logan Gunthorpe
2026-09-20 11:34     ` Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 04/18] PCI: Reject unreadable ACS controls in isolation checks Leon Romanovsky
2026-09-18 19:59   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 05/18] PCI/P2PDMA: Evaluate ACS controls at the path divergence Leon Romanovsky
2026-09-18 20:07   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 06/18] PCI/P2PDMA: Document directional ACS routing Leon Romanovsky
2026-09-18 20:53   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 07/18] PCI/P2PDMA: Collect the path's ACS controls before deciding Leon Romanovsky
2026-09-18 21:11   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 08/18] PCI/P2PDMA: Answer routing per TLP class Leon Romanovsky
2026-09-18 21:55   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 09/18] PCI/P2PDMA: Route Relaxed Ordering Completions directly Leon Romanovsky
2026-09-18 22:07   ` Logan Gunthorpe
2026-09-14 11:22 ` [PATCH v6 10/18] PCI/P2PDMA: Reject Translated Requests blocked by Translation Blocking Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 11/18] PCI/P2PDMA: Route Translated Requests under Direct Translated P2P Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 12/18] PCI/P2PDMA: Log detailed ACS routing diagnostics Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 13/18] PCI/P2PDMA: Add KUnit tests for the ACS routing decisions Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 14/18] PCI/P2PDMA: Test the ACS P2P routing walk Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 15/18] PCI: Add KUnit coverage for ACS isolation checks Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 16/18] PCI/P2PDMA: Document TLP-class routing Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 17/18] dma-buf: Let importers ask how peer-to-peer traffic is routed Leon Romanovsky
2026-09-14 14:27   ` Christian König
2026-09-14 22:10     ` Jason Gunthorpe
2026-09-15  6:28       ` Leon Romanovsky
2026-09-15  6:23     ` Leon Romanovsky
2026-09-14 11:22 ` [PATCH v6 18/18] RDMA/mlx5: Ask P2PDMA whether ATS takes a direct peer-to-peer route Leon Romanovsky
2026-09-17 13:56   ` Thomas Hellström
2026-09-17 14:00     ` Christian König
2026-09-17 14:28       ` Jason Gunthorpe
2026-09-17 14:02     ` Jason Gunthorpe
2026-09-17 14:16       ` Thomas Hellström
2026-09-17 15:15         ` Jason Gunthorpe
2026-09-18 12:15     ` Leon Romanovsky
2026-09-18 13:42       ` Thomas Hellström
2026-09-18 17:05         ` Jason Gunthorpe
2026-09-19 11:25           ` Leon Romanovsky
2026-09-21  6:43           ` Christian König
2026-09-21  6:57             ` Thomas Hellström [this message]
2026-09-21 13:08             ` Jason Gunthorpe
     [not found]           ` <f9ced8cab6eb929a5f65d789fe6922458c6f3396.camel@linux.intel.com>
     [not found]             ` <20260921131055.GP11599@ziepe.ca>
2026-09-21 13:27               ` Thomas Hellström
2026-09-21 13:25       ` Jason Gunthorpe

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