From: Jason Gunthorpe <jgg@ziepe.ca>
To: Leon Romanovsky <leon@kernel.org>
Cc: "Marek Szyprowski" <m.szyprowski@samsung.com>,
"Robin Murphy" <robin.murphy@arm.com>,
"Michael S. Tsirkin" <mst@redhat.com>,
"Petr Tesarik" <ptesarik@suse.com>,
"Jonathan Corbet" <corbet@lwn.net>,
"Shuah Khan" <skhan@linuxfoundation.org>,
"Jason Wang" <jasowang@redhat.com>,
"Xuan Zhuo" <xuanzhuo@linux.alibaba.com>,
"Eugenio Pérez" <eperezma@redhat.com>,
iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
linux-doc@vger.kernel.org, virtualization@lists.linux.dev,
linux-rdma@vger.kernel.org
Subject: Re: [PATCH 2/3] dma-mapping: Clarify valid conditions for CPU cache line overlap
Date: Mon, 9 Mar 2026 12:13:56 -0300 [thread overview]
Message-ID: <20260309151356.GN1687929@ziepe.ca> (raw)
In-Reply-To: <20260309150502.GX12611@unreal>
On Mon, Mar 09, 2026 at 05:05:02PM +0200, Leon Romanovsky wrote:
> Regarding failure on unsupported systems, I have tried more than once to
> make the RDMA fail when the device is known to take the SWIOTLB path
> in RDMA and cannot operate correctly, but each attempt was met with a
> cold reception:
> https://lore.kernel.org/all/d18c454636bf3cfdba9b66b7cc794d713eadc4a5.1719909395.git.leon@kernel.org/
I think alot of that is the APIs used there. It is hard to determine
if SWIOTLB is possible or coherent is possible, I've also hit these
things in VFIO and gave up.
However, DMA_ATTR_REQUIRE_COHERENCE can be done properly and not leak
alot of dangerous APIs to drivers (beyond itself).
It is also more important now with CC systems, I think.
Jason
next prev parent reply other threads:[~2026-03-09 15:13 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-03-07 16:49 [PATCH 0/3] RDMA: Enable runs with DMA debug enabled Leon Romanovsky
2026-03-07 16:49 ` [PATCH 1/3] dma-debug: Allow multiple invocations of overlapping entries Leon Romanovsky
2026-03-07 16:49 ` [PATCH 2/3] dma-mapping: Clarify valid conditions for CPU cache line overlap Leon Romanovsky
2026-03-08 18:19 ` Jason Gunthorpe
2026-03-08 18:49 ` Leon Romanovsky
2026-03-08 23:09 ` Jason Gunthorpe
2026-03-09 9:03 ` Leon Romanovsky
2026-03-09 12:30 ` Marek Szyprowski
2026-03-09 13:20 ` Jason Gunthorpe
2026-03-09 15:05 ` Leon Romanovsky
2026-03-09 15:13 ` Jason Gunthorpe [this message]
2026-03-10 9:45 ` Marek Szyprowski
2026-03-10 12:34 ` Jason Gunthorpe
2026-03-10 18:27 ` Leon Romanovsky
2026-03-10 21:08 ` Marek Szyprowski
2026-03-10 23:34 ` Jason Gunthorpe
2026-03-07 16:49 ` [PATCH 3/3] RDMA/umem: Tell DMA debug that cacheline overlap is expected Leon Romanovsky
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