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. Changes from 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 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 | 760 ++++++++++++++++++++++++++++++++++++++------- drivers/vhost/vhost.h | 60 +++- include/uapi/linux/vhost.h | 28 ++ 4 files changed, 790 insertions(+), 121 deletions(-) -- 2.7.4
