linux.git/drivers/virtio/virtio_ring.c, branch v5.5

virtio_ring: fix return code on DMA mapping fails

2019-11-19T10:13:49+00:00

Commit 780bc7903a32 ("virtio_ring: Support DMA APIs")  makes
virtqueue_add() return -EIO when we fail to map our I/O buffers. This is
a very realistic scenario for guests with encrypted memory, as swiotlb
may run out of space, depending on it's size and the I/O load.

The virtio-blk driver interprets -EIO form virtqueue_add() as an IO
error, despite the fact that swiotlb full is in absence of bugs a
recoverable condition.

Let us change the return code to -ENOMEM, and make the block layer
recover form these failures when virtio-blk encounters the condition
described above.

Cc: stable@vger.kernel.org
Fixes: 780bc7903a32 ("virtio_ring: Support DMA APIs")
Signed-off-by: Halil Pasic 
Tested-by: Michael Mueller 
Signed-off-by: Michael S. Tsirkin

virtio_ring: fix stalls for packed rings

2019-10-28T08:24:46+00:00

When VIRTIO_F_RING_EVENT_IDX is negotiated, virtio devices can
use virtqueue_enable_cb_delayed_packed to reduce the number of device
interrupts.  At the moment, this is the case for virtio-net when the
napi_tx module parameter is set to false.

In this case, the virtio driver selects an event offset and expects that
the device will send a notification when rolling over the event offset
in the ring.  However, if this roll-over happens before the event
suppression structure update, the notification won't be sent. To address
this race condition the driver needs to check wether the device rolled
over the offset after updating the event suppression structure.

With VIRTIO_F_RING_PACKED, the virtio driver did this by reading the
flags field of the descriptor at the specified offset.

Unfortunately, checking at the event offset isn't reliable: if
descriptors are chained (e.g. when INDIRECT is off) not all descriptors
are overwritten by the device, so it's possible that the device skipped
the specific descriptor driver is checking when writing out used
descriptors. If this happens, the driver won't detect the race condition
and will incorrectly expect the device to send a notification.

For virtio-net, the result will be a TX queue stall, with the
transmission getting blocked forever.

With the packed ring, it isn't easy to find a location which is
guaranteed to change upon the roll-over, except the next device
descriptor, as described in the spec:

        Writes of device and driver descriptors can generally be
        reordered, but each side (driver and device) are only required to
        poll (or test) a single location in memory: the next device descriptor after
        the one they processed previously, in circular order.

while this might be sub-optimal, let's do exactly this for now.

Cc: stable@vger.kernel.org
Cc: Jason Wang 
Fixes: f51f982682e2a ("virtio_ring: leverage event idx in packed ring")
Signed-off-by: Marvin Liu 
Signed-off-by: Michael S. Tsirkin

virtio_ring: fix unmap of indirect descriptors

2019-09-09T14:43:15+00:00

The function virtqueue_add_split() DMA-maps the scatterlist buffers. In
case a mapping error occurs the already mapped buffers must be unmapped.
This happens by jumping to the 'unmap_release' label.

In case of indirect descriptors the release is wrong and may leak kernel
memory. Because the implementation assumes that the head descriptor is
already mapped it starts iterating over the descriptor list starting
from the head descriptor. However for indirect descriptors the head
descriptor is never mapped in case of an error.

The fix is to initialize the start index with zero in case of indirect
descriptors and use the 'desc' pointer directly for iterating over the
descriptor chain.

Signed-off-by: Matthias Lange 
Signed-off-by: Michael S. Tsirkin

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 102

2019-05-24T15:39:00+00:00

Based on 1 normalized pattern(s):

  this program is free software you can redistribute it and or modify
  it under the terms of the gnu general public license as published by
  the free software foundation either version 2 of the license or at
  your option any later version this program is distributed in the
  hope that it will be useful but without any warranty without even
  the implied warranty of merchantability or fitness for a particular
  purpose see the gnu general public license for more details you
  should have received a copy of the gnu general public license along
  with this program if not write to the free software foundation inc
  51 franklin st fifth floor boston ma 02110 1301 usa

extracted by the scancode license scanner the SPDX license identifier

  GPL-2.0-or-later

has been chosen to replace the boilerplate/reference in 50 file(s).

Signed-off-by: Thomas Gleixner 
Reviewed-by: Kate Stewart 
Reviewed-by: Allison Randal 
Reviewed-by: Richard Fontana 
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190523091649.499889647@linutronix.de
Signed-off-by: Greg Kroah-Hartman

virtio/virtio_ring: do some comment fixes

2019-05-12T17:11:35+00:00

There are lots of mismatches between comments and codes, this
patch do these comment fixes.

Signed-off-by: Jiang Biao 
Signed-off-by: Michael S. Tsirkin

virtio_ring: Fix potential mem leak in virtqueue_add_indirect_packed

2019-05-12T17:11:35+00:00

'desc' should be freed before leaving from err handing path.

Fixes: 1ce9e6055fa0 ("virtio_ring: introduce packed ring support")
Signed-off-by: YueHaibing 
Signed-off-by: Michael S. Tsirkin 
Acked-by: Jason Wang 
stable@vger.kernel.org

virtio: Honour 'may_reduce_num' in vring_create_virtqueue

2019-04-08T21:05:52+00:00

vring_create_virtqueue() allows the caller to specify via the
may_reduce_num parameter whether the vring code is allowed to
allocate a smaller ring than specified.

However, the split ring allocation code tries to allocate a
smaller ring on allocation failure regardless of what the
caller specified. This may cause trouble for e.g. virtio-pci
in legacy mode, which does not support ring resizing. (The
packed ring code does not resize in any case.)

Let's fix this by bailing out immediately in the split ring code
if the requested size cannot be allocated and may_reduce_num has
not been specified.

While at it, fix a typo in the usage instructions.

Fixes: 2a2d1382fe9d ("virtio: Add improved queue allocation API")
Cc: stable@vger.kernel.org # v4.6+
Signed-off-by: Cornelia Huck 
Signed-off-by: Michael S. Tsirkin 
Reviewed-by: Halil Pasic 
Reviewed-by: Jens Freimann

virtio: Introduce virtio_max_dma_size()

2019-03-06T16:19:15+00:00

This function returns the maximum segment size for a single
dma transaction of a virtio device. The possible limit comes
from the SWIOTLB implementation in the Linux kernel, that
has an upper limit of (currently) 256kb of contiguous
memory it can map. Other DMA-API implementations might also
have limits.

Use the new dma_max_mapping_size() function to determine the
maximum mapping size when DMA-API is in use for virtio.

Cc: stable@vger.kernel.org
Reviewed-by: Konrad Rzeszutek Wilk 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Joerg Roedel 
Signed-off-by: Michael S. Tsirkin

virtio: drop internal struct from UAPI

2019-02-05T20:29:48+00:00

There's no reason to expose struct vring_packed in UAPI - if we do we
won't be able to change or drop it, and it's not part of any interface.

Let's move it to virtio_ring.c

Cc: Tiwei Bie 
Signed-off-by: Michael S. Tsirkin

virtio: support VIRTIO_F_ORDER_PLATFORM

2019-01-24T15:15:42+00:00

This patch introduces the support for VIRTIO_F_ORDER_PLATFORM.
If this feature is negotiated, the driver must use the barriers
suitable for hardware devices. Otherwise, the device and driver
are assumed to be implemented in software, that is they can be
assumed to run on identical CPUs in an SMP configuration. Thus
a weaker form of memory barriers is sufficient to yield better
performance.

It is recommended that an add-in card based PCI device offers
this feature for portability. The device will fail to operate
further or will operate in a slower emulation mode if this
feature is offered but not accepted.

Signed-off-by: Tiwei Bie 
Signed-off-by: Michael S. Tsirkin