This patch tries to implement an device IOTLB for vhost. This could be used with for co-operation with userspace IOMMU implementation (qemu) for a secure DMA environment (DMAR) in guest. The idea is simple. When vhost meets an IOTLB miss, it will request the assistance of userspace to do the translation, this is done through: - when there's a IOTLB miss, it will notify userspace through vhost_net fd and then userspace read the fault address, size and access from vhost fd. - userspace write the translation result back to vhost fd, vhost can then update its IOTLB. The codes were optimized for fixed mapping users e.g dpdk in guest. It will be slow if dynamic mappings were used in guest. We could do optimizations on top. The codes were designed to be architecture independent. It should be easily ported to any architecture. Stress tested with l2fwd/vfio in guest with 4K/2M/1G page size. On 1G hugepage case, 100% TLB hit rate were noticed. Have a benchmark on this. Test was done with l2fwd in guest.For 2MB page, no difference in 64B performance and I notice a 4%-5% drop for 1500B performance compare to UIO in guest. We can add some shortcut to bypass the IOTLB for virtqueue accessing, but I think it's better to do this on top. Changes from RFC V3: - rebase on latest - minor tweak on commit log - use VHOST_ACCESS_RO instead of VHOST_ACCESS_WO in vhost_copy_from_user() - switch to use atomic userspace access helper in vhost_get/put_user() - remove debug codes in vhost_iotlb_miss() - use FIFO instead of FILO when doing TLB replacement - fix unbalanced lock in vhost_process_iotlb_msg() Changes from RFC V2: - introduce memory accessors for vhost - switch from ioctls to oridinary file read/write for iotlb miss and updating - do not assume virtqueue were virtually mapped contiguously, all virtqueue access were done throug IOTLB - verify memory access during IOTLB update and fail early - introduce a module parameter for the size of IOTLB Changes from RFC V1: - support any size/range of updating and invalidation through introducing the interval tree. - convert from per device iotlb request to per virtqueue iotlb request, this solves the possible deadlock in V1. - read/write permission check support. Please review. Jason Wang (3): vhost: introduce vhost memory accessors vhost: convert pre sorted vhost memory array to interval tree vhost: device IOTLB API drivers/vhost/net.c | 63 +++- drivers/vhost/vhost.c | 799 +++++++++++++++++++++++++++++++++++++++------ drivers/vhost/vhost.h | 60 +++- include/uapi/linux/vhost.h | 28 ++ 4 files changed, 829 insertions(+), 121 deletions(-) -- 1.8.3.1 _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
