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Subject[PATCH 0/5]
Date
Hi all:

This series tries to support batched IOTLB updating vhost-vdpa.

Currently vhost-vdpa accepts userspace mapping via IOTLB API, and it
can only forward one mapping to IOMMU or device through IOMMU API or
dma_map(). Though set_map() is designed to have the capability to pass
an rbtree based mapping to vDPA device, it's still be called at least
once for each VHOST_IOTLB_UPDATE or VHOST_IOTLB_INVALIDATE. This is
because vhost-vdpa doesn't know the userspace start or stop then
updating.

So this patch introduces two flags as hints for vhost-vdpa to call
set_map() only when userspace finish a batch of IOTLB updating.

So instead of:

1) VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE -> set_map() (s)
2) VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE -> set_map() (s)
...
n) VHOST_IOTLB_UPDATE/VHOST_IOTLB_INVALIDATE -> set_map() (s)

With the help of hints, we do:

0) VHOST_IOTLB_BATCH_START

1) VHOST_IOTLB_UPDATE/INVALIDATE
...
n) VHOST_IOTLB_UPDATE/INVALIDATE

n+1) VHOST_IOTLB_BATCH_END -> set_map()

One one call of set_map() to vDPA device for a batch of IOTLB
mappings. So for the device that has its own DMA translation logic, it
can efficiently structure the memory mapping to get best performance.

Note, this only impacts the devices that want its own DMA
translation (less times of set_map() call). For other type of devices,
there's no changes in the behaviour.

Changes from RFCV1:

- tweak the comments per Michael's request

Jason Wang (5):
vhost-vdpa: refine ioctl pre-processing
vhost: generialize backend features setting/getting
vhost-vdpa: support get/set backend features
vhost-vdpa: support IOTLB batching hints
vdpasim: support batch updating

drivers/vdpa/vdpa_sim/vdpa_sim.c | 40 +++++++++++++++++++++--
drivers/vhost/net.c | 18 ++---------
drivers/vhost/vdpa.c | 55 ++++++++++++++++++++++++++------
drivers/vhost/vhost.c | 15 +++++++++
drivers/vhost/vhost.h | 2 ++
include/uapi/linux/vhost.h | 2 ++
include/uapi/linux/vhost_types.h | 11 +++++++
7 files changed, 114 insertions(+), 29 deletions(-)

--
2.20.1

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