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b743922b5a
[ Upstream commit 061a785a114f159e990ea8ed8d1b7dca4b41120f ]
Physical addresses under IOVA on x86 platform are mapped contiguously
as a side effect before the patch that removed CONFIG_DMA_REMAP. The
NTB rx buffer ring is a single chunk DMA buffer that is allocated
against the NTB PCI device. If the receive side is using a DMA device,
then the buffers are remapped against the DMA device before being
submitted via the dmaengine API. This scheme becomes a problem when
the physical memory is discontiguous. When dma_map_page() is called
on the kernel virtual address from the dma_alloc_coherent() call, the
new IOVA mapping no longer points to all the physical memory allocated
due to being discontiguous. Change dma_alloc_coherent() to dma_alloc_attrs()
in order to force DMA_ATTR_FORCE_CONTIGUOUS attribute. This is the best
fix for the circumstance. A potential future solution may be having the DMA
mapping API providing a way to alias an existing IOVA mapping to a new
device perhaps.
This fix is not to fix the patch pointed to by the fixes tag, but to fix
the issue arised in the ntb_transport driver on x86 platforms after the
said patch is applied.
Reported-by: Jerry Dai <jerry.dai@intel.com>
Fixes: f5ff79fddf ("dma-mapping: remove CONFIG_DMA_REMAP")
Tested-by: Jerry Dai <jerry.dai@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.