Re: [RFC PATCH V3 0/3] basic device IOTLB support

[Jason Wang]

On 2016å06æ22æ 00:44, Michael S. Tsirkin wrote:
> 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?

Posted, thanks.

> > 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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