passt/virtio.c, branch 2026_05_07.1afd4ed

treewide: Spell ASSERT() as assert()

2026-03-20T20:05:29+00:00

The standard library assert(3), at least with glibc, hits our seccomp
filter and dies with SIGSYS before it's able to print a message, making it
near useless.  Therefore, since 7a8ed9459dfe ("Make assertions actually
useful") we've instead used our own implementation, named ASSERT().

This makes our code look slightly odd though - ASSERT() has the same
overall effect as assert(), it's just a different implementation.  More
importantly this makes it awkward to share code between passt/pasta proper
and things that compile in a more typical environment.  We're going to want
that for our upcoming dynamic configuration tool.

Address this by overriding the standard library's assert() implementation
with our own, instead of giving ours its own name.

The standard assert() is supposed to be omitted if NDEBUG is defined,
which ours doesn't do.  Implement that as well, so ours doesn't
unexpectedly differ.  For the -DNDEBUG case we do this by *not* overriding
assert(), since it will be a no-op anyway.  This requires a few places to
add a #include  to let us compile (albeit with warnings) when
-DNDEBUG.

Signed-off-by: David Gibson 
[sbrivio: Fix some conflicts and missing conversions as a result of
 applying "vu_common: Move iovec management into vu_collect()" first]
Signed-off-by: Stefano Brivio

virtio: Pass iovec arrays as separate parameters to vu_queue_pop()

2026-03-20T19:05:12+00:00

Currently vu_queue_pop() and vu_queue_map_desc() read the iovec arrays
(in_sg/out_sg) and their sizes (in_num/out_num) from the vu_virtq_element
struct.  This couples the iovec storage to the element, requiring callers
like vu_handle_tx() to pre-initialize the element fields before calling
vu_queue_pop().

Pass the iovec arrays and their maximum sizes as separate parameters
instead.  vu_queue_map_desc() now writes the actual descriptor count
and iovec pointers back into the element after mapping, rather than
using the element as both input and output.

This decouples the iovec storage from the element, which is a
prerequisite for multi-buffer support where a single frame can span
multiple virtqueue elements sharing a common iovec pool.

No functional change.

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

treewide: Fix places where we incorrectly indented with spaces

2026-01-11T00:31:50+00:00

Had a moment to address this trivial issue.

The passt convention is to indent code with tabs (K&R / kernel style).
However there were a handful of places where we used spaces instead.  Fix
them.

Link: https://bugs.passt.top/show_bug.cgi?id=135
Reported-by: Xun Gu 
Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

packet: Refactor vhost-user memory region handling

2025-09-03T18:43:48+00:00

This patch refactors the handling of vhost-user memory regions by
introducing a new `struct vdev_memory` to encapsulate the regions
array and their count (`nregions`) within the main `vu_dev` structure.

This new `vdev_memory` structure is then passed to the packet pool by
re-using the existing `p->buf` field. A `p->buf_size` of 0 indicates
that `p->buf` holds a pointer to `struct vdev_memory` instead of a
regular packet buffer. A new helper, `get_vdev_memory()`, is added to
abstract this access pattern.

Previous implementation was using a marker at the end of the memory
regions array. We can now uses all the slots.

Signed-off-by: Laurent Vivier 
Reviewed-by: David Gibson 
Signed-off-by: Stefano Brivio

style: Fix 'Return' comment style

2025-07-18T17:19:24+00:00

We always use imperative (no 'Returns:'), no tab after the ':' and
only one space, the first character is always lowercase.

This is fixed with:

 sed -i "s/Returns:/Return:/;s/Return:    /Return: /;s/Return:  */Return: /;s/Return: \([A-Z]\)/Return: \L\1/" *.[ch]

And manually updated to fix alignment of multiline comment and words
that must keep uppercase (like IPv4, TCP, UDP, Layer-4).

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

virtio: Correct and align comment headers

2025-05-16T16:27:11+00:00

Standardize and fix issues in `virtio.c` and `virtio.h` comment headers.

Improvements include:
- Added `()` to function names in comment summaries.
- Added colons after parameter and enum member tags.
- Changed `/*` to `/**` for `virtq_avail_event()` comment.
- Fixed typos (e.g., "file"->"fill", "virqueue"->"virtqueue").
- Added missing `Return:` tag for `vu_queue_rewind()`.
- Corrected parameter names in `virtio.h` comments to match code.

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

virtio: Fix Clang warning (bugprone-sizeof-expression, cert-arr39-c)

2025-05-14T15:51:32+00:00

In `virtqueue_read_indirect_desc()`, the pointer arithmetic involving
`desc` is intentional. We add the length in bytes (`read_len`)
divided by the size of `struct vring_desc` to `desc`, which is
an array of `struct vring_desc`. This correctly calculates the
offset in terms of the number of `struct vring_desc` elements.

Clang issues the following warning due to this explicit scaling:

virtio.c:238:8: error: suspicious usage of 'sizeof(...)' in pointer
arithmetic; this scaled value will be scaled again by the '+='
operator [bugprone-sizeof-expression,cert-arr39-c,-Werror]
  238 |         desc += read_len / sizeof(struct vring_desc);
      |               ^            ~~~~~~~~~~~~~~~~~~~~~~~~~
virtio.c:238:8: note: '+=' in pointer arithmetic internally scales
with 'sizeof(struct vring_desc)' == 16

This behavior is intended, so the warning can be considered a
false positive in this context. The code correctly advances the
pointer by the desired number of descriptor entries.

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio

vhost_user: Don't export several functions

2025-03-07T01:21:24+00:00

vhost-user added several functions which are exposed in headers, but not
used outside the file where they're defined.  I can't tell if these are
really internal functions, or of they're logically supposed to be exported,
but we don't happen to have anything using them yet.

For the time being, just remove the exports.  We can add them back if we
need to.

Signed-off-by: David Gibson 
Signed-off-by: Stefano Brivio

vhost-user: add VHOST_USER_SET_LOG_BASE command

2025-01-20T18:51:24+00:00

Sets logging shared memory space.

When the back-end has VHOST_USER_PROTOCOL_F_LOG_SHMFD protocol feature,
the log memory fd is provided in the ancillary data of
VHOST_USER_SET_LOG_BASE message, the size and offset of shared memory
area provided in the message.

Signed-off-by: Laurent Vivier 
[sbrivio: Fix coding style in a bunch of places]
Signed-off-by: Stefano Brivio

vhost-user: Pass vu_dev to more virtio functions

2025-01-20T18:51:24+00:00

vu_dev will be needed to log page update.

Add the parameter to:

  vring_used_write()
  vu_queue_fill_by_index()
  vu_queue_fill()
  vring_used_idx_set()
  vu_queue_flush()

The new parameter is unused for now.

Signed-off-by: Laurent Vivier 
Signed-off-by: Stefano Brivio