linux-stable.git/drivers/virtio/virtio_ring.c, branch linux-3.9.y

virtio: make virtqueue_add_buf() returning 0 on success, not capacity.

2012-12-18T04:50:34+00:00

Now noone relies on this behavior, we simplify virtqueue_add_buf() so it
return 0 or -errno.

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

virtio: move queue_index and num_free fields into core struct virtqueue.

2012-12-18T04:50:31+00:00

They're generic concepts, so hoist them.  This also avoids accessor
functions (though kept around for merge with DaveM's net tree).

This goes even further than Jason Wang's 17bb6d4088 patch
("virtio-ring: move queue_index to vring_virtqueue") which moved the
queue_index from the specific transport.

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

virtio: force vring descriptors to be allocated from lowmem

2012-10-22T07:49:49+00:00

Virtio devices may attempt to add descriptors to a virtqueue from atomic
context using GFP_ATOMIC allocation. This is problematic because such
allocations can fall outside of the lowmem mapping, causing virt_to_phys
to report bogus physical addresses which are subsequently passed to
userspace via the buffers for the virtual device.

This patch masks out __GFP_HIGH and __GFP_HIGHMEM from the requested
flags when allocating descriptors for a virtqueue. If an atomic
allocation is requested and later fails, we will return -ENOSPC which
will be handled by the driver.

Cc: stable@kernel.org
Cc: Sasha Levin 
Signed-off-by: Will Deacon 
Signed-off-by: Rusty Russell

virtio-ring: move queue_index to vring_virtqueue

2012-09-28T05:35:15+00:00

Instead of storing the queue index in transport-specific virtio structs,
this patch moves them to vring_virtqueue and introduces an helper to get
the value.  This lets drivers simplify their management and tracing of
virtqueues.

Signed-off-by: Jason Wang 
Signed-off-by: Paolo Bonzini 
Signed-off-by: Rusty Russell

virtio: correct the memory barrier in virtqueue_kick_prepare()

2012-01-27T21:40:23+00:00

Use virtio_mb() to make sure the available index to be exposed before
checking the the avail event. Otherwise we may get stale value of
avail event in guest and never kick the host after.

Note: this fixes a bug introduced by ee7cd8981e15bcb365fc762afe3fc47b8242f630.

Signed-off-by: Jason Wang 
Acked-by: Michael S. Tsirkin 
Signed-off-by: Rusty Russell 
Cc: stable@kernel.org

virtio: fix typos of memory barriers

2012-01-27T21:40:22+00:00

Note: this fixes a bug introduced recently in
7b21e34fd1c272e3a8c3846168f2f6287a4cd72b.

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

virtio: add debugging if driver doesn't kick.

2012-01-12T05:14:43+00:00

Under the existing #ifdef DEBUG, check that they don't have more than
1/10 of a second between an add_buf() and a
virtqueue_notify()/virtqueue_kick_prepare() call.

We could get false positives on a really busy system, but good for
development.

Signed-off-by: Rusty Russell

virtio: expose added descriptors immediately.

2012-01-12T05:14:43+00:00

A virtio driver does virtqueue_add_buf() multiple times before finally
calling virtqueue_kick(); previously we only exposed the added buffers
in the virtqueue_kick() call.  This means we don't need a memory
barrier in virtqueue_add_buf(), but it reduces concurrency as the
device (ie. host) can't see the buffers until the kick.

In the unusual (but now possible) case where a driver does add_buf()
and get_buf() without doing a kick, we do need to insert one before
our counter wraps.  Otherwise we could wrap num_added, and later on
not realize that we have passed the marker where we should have
kicked.

Signed-off-by: Rusty Russell

virtio: avoid modulus operation.

2012-01-12T05:14:43+00:00

Since we know vq->vring.num is a power of 2, modulus is lazy (it's asserted
in vring_new_virtqueue()).

Signed-off-by: Rusty Russell

virtio: support unlocked queue kick

2012-01-12T05:14:43+00:00

Based on patch by Christoph for virtio_blk speedup:

	Split virtqueue_kick to be able to do the actual notification
	outside the lock protecting the virtqueue.  This patch was
	originally done by Stefan Hajnoczi, but I can't find the
	original one anymore and had to recreated it from memory.
	Pointers to the original or corrections for the commit message
	are welcome.

Stefan's patch was here:

	https://github.com/stefanha/linux/commit/a6d06644e3a58e57a774e77d7dc34c4a5a2e7496
	http://www.spinics.net/lists/linux-virtualization/msg14616.html

Third time's the charm!

Signed-off-by: Rusty Russell