linux-toradex.git/include/linux/virtio_config.h, branch v4.8-rc6

virtio: new feature to detect IOMMU device quirk

2016-08-01T18:44:52+00:00

The interaction between virtio and IOMMUs is messy.

On most systems with virtio, physical addresses match bus addresses,
and it doesn't particularly matter which one we use to program
the device.

On some systems, including Xen and any system with a physical device
that speaks virtio behind a physical IOMMU, we must program the IOMMU
for virtio DMA to work at all.

On other systems, including SPARC and PPC64, virtio-pci devices are
enumerated as though they are behind an IOMMU, but the virtio host
ignores the IOMMU, so we must either pretend that the IOMMU isn't
there or somehow map everything as the identity.

Add a feature bit to detect that quirk: VIRTIO_F_IOMMU_PLATFORM.

Any device with this feature bit set to 0 needs a quirk and has to be
passed physical addresses (as opposed to bus addresses) even though
the device is behind an IOMMU.

Note: it has to be a per-device quirk because for example, there could
be a mix of passed-through and virtual virtio devices. As another
example, some devices could be implemented by an out of process
hypervisor backend (in case of qemu vhost, or vhost-user) and so support
for an IOMMU needs to be coded up separately.

It would be cleanest to handle this in IOMMU core code, but that needs
per-device DMA ops. While we are waiting for that to be implemented, use
a work-around in virtio core.

Note: a "noiommu" feature is a quirk - add a wrapper to make
that clear.

Signed-off-by: Michael S. Tsirkin

virtio: make find_vqs() checkpatch.pl-friendly

2016-01-12T18:47:06+00:00

checkpatch.pl wants arrays of strings declared as follows:

  static const char * const names[] = { "vq-1", "vq-2", "vq-3" };

Currently the find_vqs() function takes a const char *names[] argument
so passing checkpatch.pl's const char * const names[] results in a
compiler error due to losing the second const.

This patch adjusts the find_vqs() prototype and updates all virtio
transports.  This makes it possible for virtio_balloon.c, virtio_input.c,
virtgpu_kms.c, and virtio_rpmsg_bus.c to use the checkpatch.pl-friendly
type.

Signed-off-by: Stefan Hajnoczi 
Signed-off-by: Michael S. Tsirkin 
Acked-by: Bjorn Andersson

virtio: add explicit big-endian support to memory accessors

2015-06-01T13:48:54+00:00

The current memory accessors logic is:
- little endian if little_endian
- native endian (i.e. no byteswap) if !little_endian

If we want to fully support cross-endian vhost, we also need to be
able to convert to big endian.

Instead of changing the little_endian argument to some 3-value enum, this
patch changes the logic to:
- little endian if little_endian
- big endian if !little_endian

The native endian case is handled by all users with a trivial helper. This
patch doesn't change any functionality, nor it does add overhead.

Signed-off-by: Greg Kurz 

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

virtio: introduce virtio_is_little_endian() helper

2015-06-01T13:48:49+00:00

Signed-off-by: Greg Kurz 

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

virtio: drop a useless config read

2015-04-01T04:07:14+00:00

    "virtio: core support for config generation"
fixed reading up 64 bit values, adding generation
checks for such reads.

By mistake, it left an explicit get call in place
as well. the result is that the value is read twice,
the first result is discarded.

Not a big deal since this only happens with virtio
blk and only on boot ATM, so performance isn't
affected, but let's clean it up.

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

virtio_config: reorder functions

2015-04-01T04:07:13+00:00

This simply reorders functions in virtio_config
so width access wrapper helpers are all together.
Drops an extra empty line while we are at it.

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

virtio: core support for config generation

2014-12-14T16:21:31+00:00

virtio 1.0 spec says:

Drivers MUST NOT assume reads from fields greater than 32 bits wide are
atomic, nor are reads from multiple fields: drivers SHOULD read device
configuration space fields like so:
	u32 before, after;
	do {
		before = get_config_generation(device);
		// read config entry/entries.
		after = get_config_generation(device);
	} while (after != before);

Do exactly this, for transports that support it.

Signed-off-by: Michael S. Tsirkin

virtio_config: fix virtio_cread_bytes

2014-12-11T18:04:38+00:00

virtio_cread_bytes is implemented incorrectly in case length happens to
be 2,4 or 8 bytes: transports and devices will assume it's an integer
value that has to be converted to LE format.

Let's just do multiple 1-byte reads: this also makes life easier
for transports who only need to implement 1,2,4 and 8 byte reads.

Signed-off-by: Michael S. Tsirkin

virtio: allow finalize_features to fail

2014-12-09T14:32:32+00:00

This will make it easy for transports to validate features and return
failure.

Signed-off-by: Michael S. Tsirkin

virtio_config: endian conversion for v1.0

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

We (ab)use virtio conversion functions for device-specific
config space accesses.

Based on original patches by Cornelia and Rusty.

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