From: Jason Gunthorpe <jgg@ziepe.ca>
To: David Laight <david.laight.linux@gmail.com>
Cc: "David Hu" <xuehaohu@google.com>,
"Sumit Semwal" <sumit.semwal@linaro.org>,
"Christian König" <christian.koenig@amd.com>,
"Nicolin Chen" <nicolinc@nvidia.com>,
"Leon Romanovsky" <leon@kernel.org>,
"Kevin Tian" <kevin.tian@intel.com>,
"Ankit Agrawal" <ankita@nvidia.com>,
"Alex Williamson" <alex@shazbot.org>,
linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org,
linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org,
iommu@lists.linux.dev, jmoroni@google.com, praan@google.com,
kpberry@google.com, chriscli@google.com, sashiko-bot@kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH v2] dma-buf: Split sgl into page-aligned 2G chunks
Date: Tue, 30 Jun 2026 09:38:49 -0300 [thread overview]
Message-ID: <20260630123849.GC7525@ziepe.ca> (raw)
In-Reply-To: <20260623094446.4a8fc2ed@pumpkin>
On Tue, Jun 23, 2026 at 09:44:46AM +0100, David Laight wrote:
> On Tue, 23 Jun 2026 01:54:59 +0000
> David Hu <xuehaohu@google.com> wrote:
>
> > Currently, `fill_sg_entry()` splits the scatterlist using `UINT_MAX`.
> > This creates a non-page-aligned DMA length (`0xFFFFFFFF`) for the
> > first entry, resulting in non-page-aligned DMA addresses for all
> > subsequent entries.
>
> There is a separate issue of whether this code is even needed at all.
> Where can transfers over 2G (never mind 4G) actually come from.
This is DMABUF land, you really can alocate DMABUFS of huge amounts of
physical memory, VFIO does this reliably and trivially for example. It
wouldn't come from the physical allocator.
So yes, these scenarios need to work in this code.
Jason
prev parent reply other threads:[~2026-06-30 12:38 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-21 22:21 [PATCH] dma-buf: Split sgl by largest page-aligned chunk David Hu
2026-06-22 8:13 ` David Laight
2026-06-22 21:26 ` David Hu
2026-06-23 8:25 ` David Laight
2026-06-23 21:03 ` David Hu
2026-06-23 1:54 ` [PATCH v2] dma-buf: Split sgl into page-aligned 2G chunks David Hu
2026-06-23 8:44 ` David Laight
2026-06-23 20:55 ` Pranjal Shrivastava
2026-06-23 22:53 ` David Laight
2026-06-24 14:31 ` Leon Romanovsky
2026-06-30 12:42 ` Jason Gunthorpe
2026-07-02 4:56 ` David Hu
2026-07-02 8:10 ` David Laight
2026-06-30 12:38 ` Jason Gunthorpe [this message]
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