Re: [Qemu-devel] [PATCH 0/8] VT-d: some enhancements on iotlb and tools

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Jun 27, 2017 at 05:03:31PM +0800, Peter Xu wrote:
> Patch 1: fixes a very rare PT path issue on iova value. It didn't
> break anything since it's merely not touched (only if when IOMMU
> enabled, then set one device to PT), but still better fix it.

Pls Cc HMP/QMP maintainers on interface patches.

Adding hmp interface only seems questionable to me.

Let's split this out - functionality and performance
can be separate from debugging and info.


> Patch 2-5: added "info iommu" hmp command, and implemented for VT-d.
> Meanwhile, added some statistics for iotlb.
> 
> Patch 6: introduce "x-iotlb-size" to tune iotlb size, or to turn it
> off (e.g., when we want to measure how iotlb affects one payload).
> 
> Patch 7: some refine on iotlb entry.
> 
> Patch 8: implemented MRU list algorithm for iotlb.
> 
> For the last patch, it's logically making more sense than the old
> algo, however the performance is merely the same as before (as far as
> I tested with simple netperf payloads, in either streaming, rr,
> reverse, etc.) since in most normal cases we cannot really let iotlb
> overflow especially when size is 1024 by default, e.g., guest kernel
> driver will release buffer when after used, and unstrict
> intel_iommu=on parameter will also send periodic global iotlb flush
> which will reset the whole cache. If anyone has suggestion on specific
> workload, please shoot. Anyway, I'm posting this out for review to see
> any possible comments/suggestions.
> 
> Thanks,
> 
> Peter Xu (8):
>   intel_iommu: fix VTD_PAGE_MASK
>   hmp: add info iommu
>   intel_iommu: support "info iommu"
>   intel_iommu: add iotlb/context cache statistics
>   intel_iommu: hmp: allow "-c" for "info iommu"
>   intel_iommu: let iotlb size tunable
>   intel_iommu: use access_flags for iotlb
>   intel_iommu: implement mru list for iotlb
> 
>  hmp-commands-info.hx           |  14 ++++
>  hmp.c                          |   6 ++
>  hmp.h                          |   1 +
>  hw/i386/intel_iommu.c          | 169 +++++++++++++++++++++++++++++++----------
>  hw/i386/intel_iommu_internal.h |  11 +--
>  hw/i386/trace-events           |   1 -
>  hw/i386/x86-iommu.c            |  17 +++++
>  include/hw/i386/intel_iommu.h  |  20 ++++-
>  include/hw/i386/x86-iommu.h    |   5 ++
>  include/hw/iommu.h             |   9 +++
>  stubs/Makefile.objs            |   1 +
>  stubs/iommu.c                  |   9 +++
>  12 files changed, 209 insertions(+), 54 deletions(-)
>  create mode 100644 include/hw/iommu.h
>  create mode 100644 stubs/iommu.c
> 
> -- 
> 2.7.4