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During the boot process all the PCI devices are assigned default PCI-MSI IRQ domain including VMD endpoint devices. If interrupt-remapping is enabled by IOMMU, the PCI devices except VMD get new INTEL-IR-MSI IRQ domain. And VMD is supposed to create and assign a separate VMD-MSI IRQ domain for its child devices in order to support MSI-X remapping capabilities. Now when MSI-X remapping in VMD is disabled in order to improve performance, VMD skips VMD-MSI IRQ domain assignment process to its child devices. Thus the devices behind VMD get default PCI-MSI IRQ domain instead of INTEL-IR-MSI IRQ domain when VMD creates root bus and configures child devices. As a result host OS fails to boot and DMAR errors were observed when interrupt remapping was enabled on Intel Icelake CPUs. For instance: DMAR: DRHD: handling fault status reg 2 DMAR: [INTR-REMAP] Request device [0xe2:0x00.0] fault index 0xa00 [fault reason 0x25] Blocked a compatibility format interrupt request To fix this issue, dev_msi_info struct in dev struct maintains correct value of IRQ domain. VMD will use this information to assign proper IRQ domain to its child devices when it doesn't create a separate IRQ domain. Link: https://lore.kernel.org/r/20220511095707.25403-2-nirmal.patel@linux.intel.com Signed-off-by: Nirmal Patel <nirmal.patel@linux.intel.com> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
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.