linux-kernel - Re: [PATCH v7 05/11] PCI/P2PDMA: Document DMABUF model

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Message-ID: <20251107202718.GE15456@unreal>
Date: Fri, 7 Nov 2025 22:27:18 +0200
From: Leon Romanovsky <leon@...nel.org>
To: Randy Dunlap <rdunlap@...radead.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>, Jens Axboe <axboe@...nel.dk>,
	Robin Murphy <robin.murphy@....com>, Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jonathan Corbet <corbet@....net>,
	Sumit Semwal <sumit.semwal@...aro.org>,
	Christian König <christian.koenig@....com>,
	Kees Cook <kees@...nel.org>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Ankit Agrawal <ankita@...dia.com>,
	Yishai Hadas <yishaih@...dia.com>,
	Shameer Kolothum <skolothumtho@...dia.com>,
	Kevin Tian <kevin.tian@...el.com>,
	Alex Williamson <alex@...zbot.org>,
	Krishnakant Jaju <kjaju@...dia.com>, Matt Ochs <mochs@...dia.com>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org, iommu@...ts.linux.dev,
	linux-mm@...ck.org, linux-doc@...r.kernel.org,
	linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
	linaro-mm-sig@...ts.linaro.org, kvm@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v7 05/11] PCI/P2PDMA: Document DMABUF model

On Fri, Nov 07, 2025 at 10:58:27AM -0800, Randy Dunlap wrote:
> 	
> 
> On 11/7/25 8:01 AM, Leon Romanovsky wrote:
> > On Thu, Nov 06, 2025 at 10:15:07PM -0800, Randy Dunlap wrote:
> >>
> >>
> >> On 11/6/25 6:16 AM, Leon Romanovsky wrote:
> >>> From: Jason Gunthorpe <jgg@...dia.com>
> >>>
> >>> Reflect latest changes in p2p implementation to support DMABUF lifecycle.
> >>>
> >>> Signed-off-by: Leon Romanovsky <leonro@...dia.com>
> >>> Signed-off-by: Jason Gunthorpe <jgg@...dia.com>
> >>> ---
> >>>  Documentation/driver-api/pci/p2pdma.rst | 95 +++++++++++++++++++++++++--------
> >>>  1 file changed, 72 insertions(+), 23 deletions(-)

<...>

> >>> -The second issue is that to make use of existing interfaces in Linux,
> >>> -memory that is used for P2P transactions needs to be backed by struct
> >>> -pages. However, PCI BARs are not typically cache coherent so there are
> >>> -a few corner case gotchas with these pages so developers need to
> >>> -be careful about what they do with them.
> >>> +For PCIe the routing of TLPs is well defined up until they reach a host bridge
> >>
> >> Define what TLP means?
> > 
> > In PCIe "world", TLP is very well-known and well-defined acronym, which
> > means Transaction Layer Packet.
> 
> It's your choice (or Bjorn's). I'm just reviewing...

Thanks a lot.