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When remapping hardware is configured by system software in scalable mode as Nested (PGTT=011b) and with PWSNP field Set in the PASID-table-entry, it may Set Accessed bit and Dirty bit (and Extended Access bit if enabled) in first-stage page-table entries even when second-stage mappings indicate that corresponding first-stage page-table is Read-Only. As the result, contents of pages designated by VMM as Read-Only can be modified by IOMMU via PML5E (PML4E for 4-level tables) access as part of address translation process due to DMAs issued by Guest. This disallows read-only mappings in the domain that is supposed to be used as nested parent. Reference from Sapphire Rapids Specification Update [1], errata details, SPR17. Userspace should know this limitation by checking the IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17 flag reported in the IOMMU_GET_HW_INFO ioctl. [1] https://www.intel.com/content/www/us/en/content-details/772415/content-details.html Link: https://lore.kernel.org/r/20231026044216.64964-9-yi.l.liu@intel.com Reviewed-by: Kevin Tian <kevin.tian@intel.com> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Yi Liu <yi.l.liu@intel.com> Signed-off-by: Jason Gunthorpe <jgg@nvidia.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.