Hi Alex, This is v2 of my attempt of fixing an issue we have on s390 with vfio-pci pass-through of the s390 specific virtual PCI device called ISM and used for cross LPAR communication. As the patch tries to explain the fact that vfio_test_domain_fgsp() uses an IOMMU mapping at IOVA 0 irrespective of any reserved regions causes the ISM device to go into an error state and thus becomes unusable for a KVM guest breaking pass-through. I tried to improve the background and explanation compared to v1 hope its more clear now. As for testing, I tested this based on current master on both on s390 where it skips the reserved 0x0-0x100000000 range and on an AMD Ryzen 3990X where it continues to do the test on DMA address 0 and sets domain->fgsp to true. Thanks, Niklas Schnelle Changes since v2: - Don't require region->start to be aligned but instead just that we can fit an aligned allocation (Alex) - Use Fixes tag for the introduction of reserved regions as that came after the fine grained super pages test (Alex) Changes since v1: - Reworded commit message to hopefully explain things a bit better and highlight that usually just mapping but not issuing DMAs for IOVAs in a resverved region is harmless but still breaks things with ISM devices. - Added a check for PAGE_SIZE * 2 alignment (Jason) Niklas Schnelle (1): vfio/type1: Respect IOMMU reserved regions in vfio_test_domain_fgsp() drivers/vfio/vfio_iommu_type1.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) -- 2.34.1
