linux.git/drivers/virtio/virtio_ring.c, branch v4.2

virtio: Avoid possible kernel panic if DEBUG is enabled.

2015-02-11T04:33:14+00:00

The virtqueue_add() calls START_USE() upon entry. The virtqueue_kick() is
called if vq->num_added == (1 << 16) - 1 before calling END_USE().
The virtqueue_kick_prepare() called via virtqueue_kick() calls START_USE()
upon entry, and will call panic() if DEBUG is enabled.
Move this virtqueue_kick() call to after END_USE() call.

Signed-off-by: Tetsuo Handa 
Signed-off-by: Rusty Russell

virtio_ring: coding style fix

2015-01-21T05:58:57+00:00

Most of our code has
struct foo {
}

Fix one instances where ring is inconsistent.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Rusty Russell

virtio: make VIRTIO_F_VERSION_1 a transport bit

2014-12-09T10:06:32+00:00

Activate VIRTIO_F_VERSION_1 automatically unless legacy_only
is set.

Signed-off-by: Michael S. Tsirkin

virtio: allow transports to get avail/used addresses

2014-12-09T10:05:25+00:00

For virtio-1, we can theoretically have a more complex virtqueue
layout with avail and used buffers not on a contiguous memory area
with the descriptor table. For now, it's fine for a transport driver
to stay with the old layout: It needs, however, a way to access
the locations of the avail/used rings so it can register them with
the host.

Reviewed-by: David Hildenbrand 
Signed-off-by: Cornelia Huck 

Signed-off-by: Michael S. Tsirkin

virtio_ring: switch to new memory access APIs

2014-12-09T10:05:25+00:00

Use virtioXX_to_cpu and friends for access to
all multibyte structures in memory.

Note: this is intentionally mechanical.
A follow-up patch will split long lines etc.

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

virtio: use u32, not bitmap for features

2014-12-09T10:05:23+00:00

It seemed like a good idea to use bitmap for features
in struct virtio_device, but it's actually a pain,
and seems to become even more painful when we get more
than 32 feature bits.  Just change it to a u32 for now.

Based on patch by Rusty.

Suggested-by: David Hildenbrand 
Signed-off-by: Rusty Russell 
Signed-off-by: Cornelia Huck 
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Cornelia Huck

virtio_ring: unify direct/indirect code paths.

2014-09-13T16:52:35+00:00

virtqueue_add() populates the virtqueue descriptor table from the sgs
given.  If it uses an indirect descriptor table, then it puts a single
descriptor in the descriptor table pointing to the kmalloc'ed indirect
table where the sg is populated.

Previously vring_add_indirect() did the allocation and the simple
linear layout.  We replace that with alloc_indirect() which allocates
the indirect table then chains it like the normal descriptor table so
we can reuse the core logic.

This slows down pktgen by less than 1/2 a percent (which uses direct
descriptors), as well as vring_bench, but it's far neater.

vring_bench before:
	1061485790-1104800648(1.08254e+09+/-6.6e+06)ns
vring_bench after:
	1125610268-1183528965(1.14172e+09+/-8e+06)ns

pktgen before:
   787781-796334(793165+/-2.4e+03)pps 365-369(367.5+/-1.2)Mb/sec (365530384-369498976(3.68028e+08+/-1.1e+06)bps) errors: 0

pktgen after:
   779988-790404(786391+/-2.5e+03)pps 361-366(364.35+/-1.3)Mb/sec (361914432-366747456(3.64885e+08+/-1.2e+06)bps) errors: 0

Now, if we make force indirect descriptors by turning off any_header_sg
in virtio_net.c:

pktgen before:
  713773-721062(718374+/-2.1e+03)pps 331-334(332.95+/-0.92)Mb/sec (331190672-334572768(3.33325e+08+/-9.6e+05)bps) errors: 0
pktgen after:
  710542-719195(714898+/-2.4e+03)pps 329-333(331.15+/-1.1)Mb/sec (329691488-333706480(3.31713e+08+/-1.1e+06)bps) errors: 0

Signed-off-by: Rusty Russell 
Signed-off-by: David S. Miller

virtio_ring: assume sgs are always well-formed.

2014-09-13T16:50:46+00:00

We used to have several callers which just used arrays.  They're
gone, so we can use sg_next() everywhere, simplifying the code.

On my laptop, this slowed down vring_bench by 15%:

vring_bench before:
	936153354-967745359(9.44739e+08+/-6.1e+06)ns
vring_bench after:
	1061485790-1104800648(1.08254e+09+/-6.6e+06)ns

However, a more realistic test using pktgen on a AMD FX(tm)-8320 saw
a few percent improvement:

pktgen before:
  767390-792966(785159+/-6.5e+03)pps 356-367(363.75+/-2.9)Mb/sec (356068960-367936224(3.64314e+08+/-3e+06)bps) errors: 0

pktgen after:
   787781-796334(793165+/-2.4e+03)pps 365-369(367.5+/-1.2)Mb/sec (365530384-369498976(3.68028e+08+/-1.1e+06)bps) errors: 0

Signed-off-by: Rusty Russell 
Signed-off-by: David S. Miller

virtio: virtio_break_device() to mark all virtqueues broken.

2014-04-28T02:04:13+00:00

Good for post-apocalyptic scenarios, like S/390 hotplug.

Signed-off-by: Rusty Russell

virtio: fail adding buffer on broken queues.

2014-03-13T00:57:57+00:00

Heinz points out that adding buffers to a broken virtqueue (which
should "never happen") still works.  Failing allows drivers to detect
and complain about broken devices.

Now drivers are robust, we can add this extra check.

Reported-by: Heinz Graalfs 
Signed-off-by: Rusty Russell