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The Requester ID/Process Address Space ID (PASID) combination identifies an address space distinct from the PCI bus address space, e.g., an address space defined by an IOMMU. But the PCIe fabric routes Memory Requests based on the TLP address, ignoring any PASID (PCIe r6.0, sec 2.2.10.4), so a TLP with PASID that SHOULD go upstream to the IOMMU may instead be routed as a P2P Request if its address falls in a bridge window. To ensure that all Memory Requests with PASID are routed upstream, only enable PASID if ACS P2P Request Redirect and Upstream Forwarding are enabled for the path leading to the device. Suggested-by: Jason Gunthorpe <jgg@nvidia.com> Suggested-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Acked-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Tested-by: Tony Zhu <tony.zhu@intel.com> Link: https://lore.kernel.org/r/20221031005917.45690-5-baolu.lu@linux.intel.com Signed-off-by: Joerg Roedel <jroedel@suse.de>
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.