linux.git/drivers/vhost/vhost.h, branch v4.4

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

vhost: cross-endian support for legacy devices

2015-06-01T13:48:55+00:00

This patch brings cross-endian support to vhost when used to implement
legacy virtio devices. Since it is a relatively rare situation, the
feature availability is controlled by a kernel config option (not set
by default).

The vq->is_le boolean field is added to cache the endianness to be
used for ring accesses. It defaults to native endian, as expected
by legacy virtio devices. When the ring gets active, we force little
endian if the device is modern. When the ring is deactivated, we
revert to the native endian default.

If cross-endian was compiled in, a vq->user_be boolean field is added
so that userspace may request a specific endianness. This field is
used to override the default when activating the ring of a legacy
device. It has no effect on modern devices.

Signed-off-by: Greg Kurz 

Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Cornelia Huck 
Reviewed-by: David Gibson

virtio: add explicit big-endian support to memory accessors

2015-06-01T13:48:54+00:00

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz 

Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Cornelia Huck 
Reviewed-by: David Gibson

vhost: introduce vhost_is_little_endian() helper

2015-06-01T13:48:53+00:00

Signed-off-by: Greg Kurz 

Signed-off-by: Michael S. Tsirkin 
Acked-by: Cornelia Huck 
Reviewed-by: David Gibson

vhost: remove unnecessary forward declarations in vhost.h

2014-12-09T10:06:33+00:00

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

vhost: add memory access wrappers

2014-12-09T10:05:29+00:00

Add guest memory access wrappers to handle virtio endianness
conversions.

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

vhost: make features 64 bit

2014-12-09T10:05:28+00:00

We need to use bit 32 for virtio 1.0.
Make vhost_has_feature bool to avoid discarding high bits.

Cc: Sergei Shtylyov 
Cc: Ben Hutchings 
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Jason Wang

vhost: move memory pointer to VQs

2014-06-09T13:21:07+00:00

commit 2ae76693b8bcabf370b981cd00c36cd41d33fabc
    vhost: replace rcu with mutex
replaced rcu sync for memory accesses with VQ mutex locl/unlock.
This is correct since all accesses are under VQ mutex, but incomplete:
we still do useless rcu lock/unlock operations, someone might copy this
code into some other context where this won't be right.
This use of RCU is also non standard and hard to understand.
Let's copy the pointer to each VQ structure, this way
the access rules become straight-forward, and there's
no need for RCU anymore.

Reported-by: Eric Dumazet 
Signed-off-by: Michael S. Tsirkin

vhost: move acked_features to VQs

2014-06-09T13:21:06+00:00

Refactor code to make sure features are only accessed
under VQ mutex. This makes everything simpler, no need
for RCU here anymore.

Signed-off-by: Michael S. Tsirkin