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Commitd850c2ee5f("iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions") created a direct-mapped reserved memory region in order to replace the static identity mapping of the ISA address space, where the latter was then removed in commitdf4f3c603a("iommu/vt-d: Remove static identity map code"). According to the history of this code and the Kconfig option surrounding it, this direct mapping exists for the benefit of legacy ISA drivers that are not compatible with the DMA API. In conjuntion with commit9b77e5c798("vfio/type1: check dma map request is within a valid iova range") this change introduced a regression where the vfio IOMMU backend enforces reserved memory regions per IOMMU group, preventing userspace from creating IOMMU mappings conflicting with prescribed reserved regions. A necessary prerequisite for the vfio change was the introduction of "relaxable" direct mappings introduced by commitadfd373820("iommu: Introduce IOMMU_RESV_DIRECT_RELAXABLE reserved memory regions"). These relaxable direct mappings provide the same identity mapping support in the default domain, but also indicate that the reservation is software imposed and may be relaxed under some conditions, such as device assignment. Convert the ISA bridge direct-mapped reserved region to relaxable to reflect that the restriction is self imposed and need not be enforced by drivers such as vfio. Fixes:1c5c59fbad("iommu/vt-d: Differentiate relaxable and non relaxable RMRRs") Cc: stable@vger.kernel.org # v5.3+ Link: https://lore.kernel.org/linux-iommu/20191211082304.2d4fab45@x1.home Reported-by: cprt <cprt@protonmail.com> Tested-by: cprt <cprt@protonmail.com> Signed-off-by: Alex Williamson <alex.williamson@redhat.com> Acked-by: Lu Baolu <baolu.lu@linux.intel.com> Reviewed-by: Eric Auger <eric.auger@redhat.com> Tested-by: Jerry Snitselaar <jsnitsel@redhat.com> Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.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.