linux-toradex.git/drivers/vhost/vhost.h, branch v4.10

vhost: cache used event for better performance

2016-12-15T22:12:50+00:00

When event index was enabled, we need to fetch used event from
userspace memory each time. This userspace fetch (with memory
barrier) could be saved sometime when 1) caching used event and 2)
if used event is ahead of new and old to new updating does not cross
it, we're sure there's no need to notify guest.

This will be useful for heavy tx load e.g guest pktgen test with Linux
driver shows ~3.5% improvement.

Signed-off-by: Jason Wang 
Signed-off-by: Michael S. Tsirkin

vhost: new device IOTLB API

2016-08-02T13:53:54+00:00

This patch tries to implement an device IOTLB for vhost. This could be
used with userspace(qemu) implementation of DMA remapping
to emulate an IOMMU for the guest.

The idea is simple, cache the translation in a software device IOTLB
(which is implemented as an interval tree) in vhost and use vhost_net
file descriptor for reporting IOTLB miss and IOTLB
update/invalidation. When vhost meets an IOTLB miss, the fault
address, size and access can be read from the file. After userspace
finishes the translation, it writes the translated address to the
vhost_net file to update the device IOTLB.

When device IOTLB is enabled by setting VIRTIO_F_IOMMU_PLATFORM all vq
addresses set by ioctl are treated as iova instead of virtual address and
the accessing can only be done through IOTLB instead of direct userspace
memory access. Before each round or vq processing, all vq metadata is
prefetched in device IOTLB to make sure no translation fault happens
during vq processing.

In most cases, virtqueues are contiguous even in virtual address space.
The IOTLB translation for virtqueue itself may make it a little
slower. We might add fast path cache on top of this patch.

Signed-off-by: Jason Wang 
[mst: use virtio feature bit: VHOST_F_DEVICE_IOTLB -> VIRTIO_F_IOMMU_PLATFORM ]
[mst: fix build warnings ]
Signed-off-by: Michael S. Tsirkin 
[ weiyj.lk: missing unlock on error ]
Signed-off-by: Wei Yongjun

vhost: convert pre sorted vhost memory array to interval tree

2016-08-01T23:57:31+00:00

Current pre-sorted memory region array has some limitations for future
device IOTLB conversion:

1) need extra work for adding and removing a single region, and it's
   expected to be slow because of sorting or memory re-allocation.
2) need extra work of removing a large range which may intersect
   several regions with different size.
3) need trick for a replacement policy like LRU

To overcome the above shortcomings, this patch convert it to interval
tree which can easily address the above issue with almost no extra
work.

The patch could be used for:

- Extend the current API and only let the userspace to send diffs of
  memory table.
- Simplify Device IOTLB implementation.

Signed-off-by: Jason Wang 
Signed-off-by: Michael S. Tsirkin

vhost: lockless enqueuing

2016-08-01T18:44:51+00:00

We use spinlock to synchronize the work list now which may cause
unnecessary contentions. So this patch switch to use llist to remove
this contention. Pktgen tests shows about 5% improvement:

Before:
~1300000 pps
After:
~1370000 pps

Signed-off-by: Jason Wang 
Reviewed-by: Michael S. Tsirkin 
Signed-off-by: Michael S. Tsirkin

vhost_net: basic polling support

2016-03-11T00:18:53+00:00

This patch tries to poll for new added tx buffer or socket receive
queue for a while at the end of tx/rx processing. The maximum time
spent on polling were specified through a new kind of vring ioctl.

Signed-off-by: Jason Wang 
Signed-off-by: Michael S. Tsirkin

vhost: introduce vhost_vq_avail_empty()

2016-03-11T00:18:50+00:00

This patch introduces a helper which will return true if we're sure
that the available ring is empty for a specific vq. When we're not
sure, e.g vq access failure, return false instead. This could be used
for busy polling code to exit the busy loop.

Signed-off-by: Jason Wang 
Signed-off-by: Michael S. Tsirkin

vhost: introduce vhost_has_work()

2016-03-11T00:18:45+00:00

This path introduces a helper which can give a hint for whether or not
there's a work queued in the work list. This could be used for busy
polling code to exit the busy loop.

Signed-off-by: Jason Wang 
Signed-off-by: Michael S. Tsirkin

vhost: rename vhost_init_used()

2016-03-02T15:02:04+00:00

Looking at how callers use this, maybe we should just rename init_used
to vhost_vq_init_access. The _used suffix was a hint that we
access the vq used ring. But maybe what callers care about is
that it must be called after access_ok.

Also, this function manipulates the vq->is_le field which isn't related
to the vq used ring.

This patch simply renames vhost_init_used() to vhost_vq_init_access() as
suggested by Michael.

No behaviour change.

Signed-off-by: Greg Kurz 
Signed-off-by: Michael S. Tsirkin

vhost: fix performance on LE hosts

2015-10-28T03:17:03+00:00

commit 2751c9882b947292fcfb084c4f604e01724af804 ("vhost: cross-endian
support for legacy devices") introduced a minor regression: even with
cross-endian disabled, and even on LE host, vhost_is_little_endian is
checking is_le flag so there's always a branch.

To fix, simply check virtio_legacy_is_little_endian first.

Cc: Greg Kurz 
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Greg Kurz 
Signed-off-by: David S. Miller

vhost: move features to core

2015-09-16T09:48:07+00:00

virtio 1 and any layout are core features, move them
there. This fixes vhost test.

Signed-off-by: Michael S. Tsirkin