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authorNiklas Schnelle <schnelle@linux.ibm.com>2023-01-10 17:44:27 +0100
committerAlex Williamson <alex.williamson@redhat.com>2023-01-10 10:44:37 -0700
commit895c0747f726bb50c9b7a805613a61d1b6f9fa06 (patch)
tree2542efa3c8697547dbf972b5fb9fc29aadb1264e /virt
parentb7bfaa761d760e72a969d116517eaa12e404c262 (diff)
vfio/type1: Respect IOMMU reserved regions in vfio_test_domain_fgsp()
Since commit cbf7827bc5dc ("iommu/s390: Fix potential s390_domain aperture shrinking") the s390 IOMMU driver uses reserved regions for the system provided DMA ranges of PCI devices. Previously it reduced the size of the IOMMU aperture and checked it on each mapping operation. On current machines the system denies use of DMA addresses below 2^32 for all PCI devices. Usually mapping IOVAs in a reserved regions is harmless until a DMA actually tries to utilize the mapping. However on s390 there is a virtual PCI device called ISM which is implemented in firmware and used for cross LPAR communication. Unlike real PCI devices this device does not use the hardware IOMMU but inspects IOMMU translation tables directly on IOTLB flush (s390 RPCIT instruction). If it detects IOVA mappings outside the allowed ranges it goes into an error state. This error state then causes the device to be unavailable to the KVM guest. Analysing this we found that vfio_test_domain_fgsp() maps 2 pages at DMA address 0 irrespective of the IOMMUs reserved regions. Even if usually harmless this seems wrong in the general case so instead go through the freshly updated IOVA list and try to find a range that isn't reserved, and fits 2 pages, is PAGE_SIZE * 2 aligned. If found use that for testing for fine grained super pages. Fixes: af029169b8fd ("vfio/type1: Check reserved region conflict and update iova list") Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com> Reviewed-by: Matthew Rosato <mjrosato@linux.ibm.com> Reviewed-by: Jason Gunthorpe <jgg@nvidia.com> Link: https://lore.kernel.org/r/20230110164427.4051938-2-schnelle@linux.ibm.com Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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