On Wed, Jan 14, 2026 at 07:48:39PM +0100, Eugenio Pérez wrote: > Address Space IDs allows the VDUSE framework to support devices able to > expose different virtqueues to different part of the drivers. For > example, to let QEMU handle the net device control virtqueue, so QEMU > always knows the state of the device like mac address or number of > queues enabled, while leaving the dataplane passtrhough to the guest
passthrough > intact. This enables live migration. > > Expands the VDUSE documentation to explain how to use the new ioctls or > the new struct members of old ioctls. > > Signed-off-by: Eugenio Pérez <[email protected]> > --- > v12: New in V12. Requested by Jason. > --- > Documentation/userspace-api/vduse.rst | 49 +++++++++++++++++++++++++++ > 1 file changed, 49 insertions(+) > > diff --git a/Documentation/userspace-api/vduse.rst > b/Documentation/userspace-api/vduse.rst > index bdb880e01132..66110d918815 100644 > --- a/Documentation/userspace-api/vduse.rst > +++ b/Documentation/userspace-api/vduse.rst > @@ -230,4 +230,53 @@ able to start the dataplane processing as follows: > 5. Inject an interrupt for specific virtqueue with the VDUSE_INJECT_VQ_IRQ > ioctl > after the used ring is filled. > > +Enabling ASID (API version 1) > +------------------------------ > + > +VDUSE supports per-address-space identifiers (ASIDs) starting with API > +version 1. Setup it Set it up > with ioctl(VDUSE_SET_API_VERSION) on `/dev/vduse/control` and > +pass `VDUSE_API_VERSION_1` before creating a new VDUSE instance with > +ioctl(VDUSE_CREATE_DEV). > + > +Afterwards, you can use the member asid of ioctl(VDUSE_IOTLB_GET_INFO) to > +select the address space of the IOTLB you are queryng. querying > Similarly, you can use > +ioctl(VDUSE_IOTLB_GET_FD2) to obtain the file descriptor describing an IOVA > +region of an specific ASID. Example usage: a specific > + > +.. code-block:: c > + > + static void *iova_to_va(int dev_fd, uint32_t asid, uint64_t iova, > + uint64_t *len) > + { > + int fd; > + void *addr; > + size_t size; > + struct vduse_iotlb_entry_v2 entry = { 0 }; > + > + entry.v1.start = iova; > + entry.v1.last = iova; > + entry.asid = asid; > + > + fd = ioctl(dev_fd, VDUSE_IOTLB_GET_FD2, &entry); > + if (fd < 0) > + return NULL; > + > + size = entry.v1.last - entry.v1.start + 1; > + *len = entry.v1.last - iova + 1; > + addr = mmap(0, size, perm_to_prot(entry.v1.perm), MAP_SHARED, > + fd, entry.v1.offset); > + close(fd); > + if (addr == MAP_FAILED) > + return NULL; > + > + /* > + * Using some data structures such as linked list to store > + * the iotlb mapping. The munmap(2) should be called for the > + * cached mapping when the corresponding VDUSE_UPDATE_IOTLB > + * message is received or the device is reset. > + */ > + > + return addr + iova - entry.start; > + } > + > For more details on the uAPI, please see include/uapi/linux/vduse.h. > -- > 2.52.0
