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INTEL_IOMMU_FLOPPY_WA workaround was introduced to create direct mappings for first 16MB for floppy devices as the floppy drivers were not using dma apis. We need not do this direct map if floppy driver is not enabled. INTEL_IOMMU_FLOPPY_WA is generally not a good idea. Iommu will be mapping pages in this address range while kernel would also be allocating from this range(mostly on memory stress). A misbehaving device using this domain will have access to the pages that the kernel might be actively using. We noticed this while running a test that was trying to figure out if any pages used by kernel is in iommu page tables. This patch reduces the scope of the above issue by disabling the workaround when floppy driver is not enabled. But we would still need to fix the floppy driver to use dma apis so that we need not do direct map without reserving the pages. Or the other option is to reserve this memory range in firmware so that kernel will not use the pages. Fixes:d850c2ee5f("iommu/vt-d: Expose ISA direct mapping region via iommu_get_resv_regions") Fixes:49a0429e53("Intel IOMMU: Iommu floppy workaround") Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org> Link: https://lore.kernel.org/r/20251002161625.1155133-1-vineeth@bitbyteword.org Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com> Signed-off-by: Joerg Roedel <joerg.roedel@amd.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 reStructuredText 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.