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Date: Tue, 19 May 2026 09:17:58 +0200
From: Christoph Hellwig <hch@lst.de>
To: Mikhail Gavrilov <mikhail.v.gavrilov@gmail.com>
Cc: Leon Romanovsky <leon@kernel.org>, m.szyprowski@samsung.com, hch@lst.de,
	robin.murphy@arm.com, djbw@kernel.org, akpm@linux-foundation.org,
	catalin.marinas@arm.com, harry@kernel.org, ming.lei@redhat.com,
	iommu@lists.linux.dev, linux-kernel@vger.kernel.org,
	Keith Busch <kbusch@kernel.org>
Subject: Re: [PATCH] dma-debug: skip cacheline overlap tracking on
 cache-coherent architectures
Message-ID: <20260519071758.GB10037@lst.de>
References: <20260518113251.64844-1-mikhail.v.gavrilov@gmail.com> <20260518121047.GR33515@unreal> <CABXGCsMxZ7VieyzWEmpGdxohdbTJ_qf_1ZOw0eF5g9i0YeOc3w@mail.gmail.com> <20260518125330.GT33515@unreal> <CABXGCsMA+uZtoup+QtGsPQcyF6TZimxYFOR2sDQksNkLpJq+2g@mail.gmail.com>
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On Mon, May 18, 2026 at 06:29:11PM +0500, Mikhail Gavrilov wrote:
> DIO from userspace is unfixable from the kernel side per that
> message; raid1 acknowledged as needing a fix Christoph didn't have.
> Two years on, those cases (plus dm-thin and io_uring polled tests
> from Ming Lei's report) still don't have an annotation path. This
> patch covers what annotation can't reach without preventing future
> annotation work.

It is not.  We could require direct I/O to/from devices that are
attached without DMA coherence to require cache line alignment.

Now that Keith pushed down the checking into the driver that's even
fairly easily doable.