linux-stable.git/drivers/virtio/virtio_ring.c, branch linux-3.0.y

virtio: support unlocked queue poll

2013-08-04T07:43:40+00:00

commit cc229884d3f77ec3b1240e467e0236c3e0647c0c upstream.

This adds a way to check ring empty state after enable_cb outside any
locks. Will be used by virtio_net.

Note: there's room for more optimization: caller is likely to have a
memory barrier already, which means we might be able to get rid of a
barrier here.  Deferring this optimization until we do some
benchmarking.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: David S. Miller 
[wg: Backported to 3.2]
Signed-off-by: Wolfram Gloger 
Signed-off-by: Greg Kroah-Hartman

virtio: force vring descriptors to be allocated from lowmem

2013-01-11T17:03:36+00:00

commit b92b1b89a33c172c075edccf6afb0edc41d851fd upstream.

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.

Signed-off-by: Will Deacon 
Cc: Sasha Levin 
Signed-off-by: Rusty Russell 
Signed-off-by: Greg Kroah-Hartman

virtio: add api for delayed callbacks

2011-05-30T01:44:16+00:00

Add an API that tells the other side that callbacks
should be delayed until a lot of work has been done.
Implement using the new event_idx feature.

Note: it might seem advantageous to let the drivers
ask for a callback after a specific capacity has
been reached. However, as a single head can
free many entries in the descriptor table,
we don't really have a clue about capacity
until get_buf is called. The API is the simplest
to implement at the moment, we'll see what kind of
hints drivers can pass when there's more than one
user of the feature.

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

virtio_ring: support event idx feature

2011-05-30T01:44:15+00:00

Support for the new event idx feature:
1. When enabling interrupts, publish the current avail index
   value to the host to get interrupts on the next update.
2. Use the new avail_event feature to reduce the number
   of exits from the guest.

Simple test with the simulator:

[virtio]# time ./virtio_test
spurious wakeus: 0x7

real    0m0.169s
user    0m0.140s
sys     0m0.019s
[virtio]# time ./virtio_test --no-event-idx
spurious wakeus: 0x11

real    0m0.649s
user    0m0.295s
sys     0m0.335s

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

virtio: Decrement avail idx on buffer detach

2011-04-21T13:27:00+00:00

When detaching a buffer from a vq, the avail.idx value should be
decremented as well.

This was noticed by hot-unplugging a virtio console port and then
plugging in a new one on the same number (re-using the vqs which were
just 'disowned').  qemu reported

   'Guest moved used index from 0 to 256'

when any IO was attempted on the new port.

CC: stable@kernel.org
Reported-by: juzhang 
Signed-off-by: Amit Shah 
Signed-off-by: Rusty Russell

virtio: return correct capacity to users

2010-11-24T04:51:11+00:00

We can't rely on indirect buffers for capacity
calculations because they need a memory allocation
which might fail.  In particular, virtio_net can get
into this situation under stress, and it drops packets
and performs badly.

So return the number of buffers we can guarantee users.

Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Rusty Russell 
Reported-By: Krishna Kumar2

virtio: fix oops on OOM

2010-07-26T15:05:31+00:00

virtio ring was changed to return an error code on OOM,
but one caller was missed and still checks for vq->vring.num.
The fix is just to check for <0 error code.

Long term it might make sense to change goto add_head to
just return an error on oom instead, but let's apply
a minimal fix for 2.6.35.

Reported-by: Chris Mason 
Signed-off-by: Michael S. Tsirkin 
Signed-off-by: Rusty Russell 
Tested-by: Chris Mason 
Cc: stable@kernel.org # .34.x
Signed-off-by: Linus Torvalds

virtio: return ENOMEM on out of memory

2010-06-23T13:19:06+00:00

add_buf returns ring size on out of memory,
this is not what devices expect.

Signed-off-by: Michael S. Tsirkin 
Acked-by: Amit Shah 
Signed-off-by: Rusty Russell 
Cc: stable@kernel.org # .34.x

virtio: add_buf_gfp

2010-05-19T12:45:46+00:00

Add an add_buf variant that gets gfp parameter. Use that
to allocate indirect buffers.

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

virtio_ring: remove a level of indirection

2010-05-19T12:45:43+00:00

We have a single virtqueue_ops implementation,
and it seems unlikely we'll get another one
at this point. So let's remove an unnecessary
level of indirection: it would be very easy to
re-add it if another implementation surfaces.

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