passt/virtio.c, branch bug165c

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

virtio: Use const pointer for vu_dev

2025-01-05T22:48:59+00:00

We don't modify the structure in some virtio functions.

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

Fix build on 32bit target

2024-11-27T15:49:21+00:00

Fix the following errors when built with CFLAGS="-m32 -U__AVX2__":

packet.c:57:23: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 5 has type ‘size_t’ {aka ‘unsigned int’} [-Wformat=]
   57 |                 trace("packet offset plus length %lu from size %lu, "
   58 |                       "%s:%i", start - p->buf + len + offset,
      |                                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      |                                                     |
      |                                                     size_t {aka unsigned int}

packet.c:57:23: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 6 has type ‘size_t’ {aka ‘unsigned int’} [-Wformat=]
   57 |                 trace("packet offset plus length %lu from size %lu, "
      |                       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   58 |                       "%s:%i", start - p->buf + len + offset,
   59 |                       p->buf_size, func, line);
      |                       ~~~~~~~~~~~
      |                        |
      |                        size_t {aka unsigned int}

vhost_user.c:139:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  139 |                         return (void *)(qemu_addr - r->qva + r->mmap_addr +
      |                                ^

vhost_user.c:439:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  439 |                         munmap((void *)r->mmap_addr, r->size + r->mmap_offset);
      |                                ^

vhost_user.c:900:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  900 |                         munmap((void *)r->mmap_addr, r->size + r->mmap_offset);
      |                                ^

virtio.c:111:32: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
  111 |                         return (void *)(guest_addr - r->gpa + r->mmap_addr +
      |                                ^

vu_common.c:37:27: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
   37 |                 char *m = (char *)dev_region->mmap_addr;
      |                           ^

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

virtio: check if avail ring is configured

2024-11-27T15:49:21+00:00

If the connection to the vhost-user front end is closed during transfers
virtio rings are deconfigured and not available anymore, but we can
try to access them to process queued data. This can trigger a SIGSEG as
we try to access unavailable memory.
To fix that check vq->vring.avail is sane before accessing the vring

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