treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 482

Based on 1 normalized pattern(s):

this work is licensed under the terms of the gnu gpl version 2

extracted by the scancode license scanner the SPDX license identifier

GPL-2.0-only

has been chosen to replace the boilerplate/reference in 48 file(s).

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Reviewed-by: Enrico Weigelt <info@metux.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190604081204.624030236@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

ringtest: support test specific parameters

Add a new flag for passing test-specific parameters.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

ringtest: fix an assert statement

There is an || vs && typo so the assert can never be triggered.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>

ringtest: poll for new buffers once before updating event index

Updating the event index has a memory barrier and causes more work
on the other side to actually signal the event. It is unnecessary
if a new buffer has already appeared on the ring, so poll once before
doing the update.

The effect of this on the 0.9 ring implementation is pretty much
invisible, but on the new-style ring it provides a consistent 3%
performance improvement.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

ringtest: commonize implementation of poll_avail/poll_used

Provide new primitives used_empty/avail_empty and
build poll_avail/poll_used on top of it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

ringtest: use link-time optimization

By using -flto and -fwhole-program, all functions from the ring implementation
can be treated as static and possibly inlined. Force this to happen through
the GCC flatten attribute.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

ringtest: pass buf != NULL

just a stub pointer for now.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

tools/virtio: add ringtest utilities

This adds micro-benchmarks useful for tuning virtio ring layouts.
Three layouts are currently implemented:

- virtio 0.9 compatible one
- an experimental extension bypassing the ring index, polling ring
itself instead
- an experimental extension bypassing avail and used ring completely

Typical use:

sh run-on-all.sh perf stat -r 10 --log-fd 1 -- ./ring

It doesn't depend on the kernel directly, but it's handy
to have as much virtio stuff as possible in one tree.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>