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[ Upstream commit121660bba6] Previously the AMD IOMMU would only enable SWIOTLB in certain circumstances: * IOMMU in passthrough mode * SME enabled This logic however doesn't work when an untrusted device is plugged in that doesn't do page aligned DMA transactions. The expectation is that a bounce buffer is used for those transactions. This fails like this: swiotlb buffer is full (sz: 4096 bytes), total 0 (slots), used 0 (slots) That happens because the bounce buffers have been allocated, followed by freed during startup but the bounce buffering code expects that all IOMMUs have left it enabled. Remove the criteria to set up bounce buffers on AMD systems to ensure they're always available for supporting untrusted devices. Fixes:82612d66d5("iommu: Allow the dma-iommu api to use bounce buffers") Suggested-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> Reviewed-by: Robin Murphy <robin.murphy@arm.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220404204723.9767-2-mario.limonciello@amd.com Signed-off-by: Joerg Roedel <jroedel@suse.de> 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.