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[ Upstream commit50310600eb] PCI ACS is disabled if Intel IOMMU is off by default or intel_iommu=off is used in command line. Unfortunately, Intel IOMMU will be forced on if there're devices sitting on an external facing PCI port that is marked as untrusted (for example, thunderbolt peripherals). That means, PCI ACS is disabled while Intel IOMMU is forced on to isolate those devices. As the result, the devices of an MFD will be grouped by a single group even the ACS is supported on device. [ 0.691263] pci 0000:00:07.1: Adding to iommu group 3 [ 0.691277] pci 0000:00:07.2: Adding to iommu group 3 [ 0.691292] pci 0000:00:07.3: Adding to iommu group 3 Fix it by requesting PCI ACS when Intel IOMMU is detected with platform opt in hint. Fixes:89a6079df7("iommu/vt-d: Force IOMMU on for platform opt in hint") Co-developed-by: Lalithambika Krishnakumar <lalithambika.krishnakumar@intel.com> Signed-off-by: Lalithambika Krishnakumar <lalithambika.krishnakumar@intel.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com> Cc: Mika Westerberg <mika.westerberg@linux.intel.com> Cc: Ashok Raj <ashok.raj@intel.com> Link: https://lore.kernel.org/r/20200622231345.29722-5-baolu.lu@linux.intel.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.