Following Will & Robin's suggestions, this series attempts to propose an alternative to [1] where the host would arbitrarily decide the location of the IOVA MSI window and would be able to report to the userspace the list of reserved IOVA regions that cannot be used along with VFIO_IOMMU_MAP_DMA. This would allow the userspace to react in case of conflict.
Userspace can retrieve all the reserved regions through the VFIO_IOMMU_GET_INFO IOCTL by querying the new RESV_IOVA_RANGE chained capability. Each reserved IOVA range is put in a separate capability. At IOMMU level, the reserved regions are stored in an iommu_domain list which is populated on each device attachment. An IOMMU add_reserved_regions callback specializes the registration of the reserved regions. On x86, the [FEE0_0000h - FEF0_000h] MSI window is registered (NOT tested). On ARM, the PCI host bridge windows (ACS check to be added?) + the MSI IOVA reserved regions are populated by the arm-smmu driver. Currently the MSI IOVA region is arbitrarily located at 0x8000000 and 1MB sized. An IOVA domain is created in add_reserved_regions callback. Then MSIs are transparently mapped using this IOVA domain. This series currently does not address some features addressed in [1]: - MSI IOVA size requirement computation - IRQ safety assessment This RFC was just tested on ARM Overdrive with QEMU and is sent to help potential discussions at LPC. Additionnal development + testing is needed. 2 tentative fixes may be submitted separately: - vfio: fix vfio_info_cap_add/shift - iommu/iova: fix __alloc_and_insert_iova_range Best Regards Eric [1] [PATCH v14 00/16] KVM PCIe/MSI passthrough on ARM/ARM64 https://lkml.org/lkml/2016/10/12/347 Git: complete series available at https://github.com/eauger/linux/tree/v4.9-rc3-reserved-rfc Eric Auger (7): vfio: fix vfio_info_cap_add/shift iommu/iova: fix __alloc_and_insert_iova_range iommu: Add a list of iommu_reserved_region in iommu_domain vfio/type1: Introduce RESV_IOVA_RANGE capability iommu: Handle the list of reserved regions iommu/vt-d: Implement add_reserved_regions callback iommu/arm-smmu: implement add_reserved_regions callback Robin Murphy (1): iommu/dma: Allow MSI-only cookies drivers/iommu/arm-smmu.c | 63 +++++++++++++++++++++++++++++++++++++++++ drivers/iommu/dma-iommu.c | 39 +++++++++++++++++++++++++ drivers/iommu/intel-iommu.c | 48 ++++++++++++++++++++++--------- drivers/iommu/iommu.c | 25 ++++++++++++++++ drivers/iommu/iova.c | 2 +- drivers/vfio/vfio.c | 5 ++-- drivers/vfio/vfio_iommu_type1.c | 63 ++++++++++++++++++++++++++++++++++++++++- include/linux/dma-iommu.h | 9 ++++++ include/linux/iommu.h | 23 +++++++++++++++ include/uapi/linux/vfio.h | 16 ++++++++++- 10 files changed, 275 insertions(+), 18 deletions(-) -- 1.9.1
