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SubjectRe: [RFC PATCH V3 0/3] basic device IOTLB support
On Tue, May 24, 2016 at 05:36:22PM +0800, Jason Wang wrote:
> 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.

Nice, this looks good to me. Can you post a non-rfc please?


> 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

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