On Mon, Jan 19, 2026 at 3:40 PM Eugenio Perez Martin <[email protected]> wrote: > > On Mon, Jan 19, 2026 at 8:19 AM Jason Wang <[email protected]> wrote: > > > > On Fri, Jan 16, 2026 at 10:05 PM Eugenio Pérez <[email protected]> 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 passthrough to the guest > > > 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]> > > > --- > > > v13: > > > * Fix s/VDUSE_IOTLB_GET_INFO/VDUSE_VQ_SETUP/. > > > * Document VDUSE_SET_VQ_GROUP_ASID VDUSE message (Jason). > > > * Fix typos (MST and Jason). > > > > > > v12: New in V12. Requested by Jason. > > > --- > > > Documentation/userspace-api/vduse.rst | 53 +++++++++++++++++++++++++++ > > > 1 file changed, 53 insertions(+) > > > > > > diff --git a/Documentation/userspace-api/vduse.rst > > > b/Documentation/userspace-api/vduse.rst > > > index bdb880e01132..aa067da92cf5 100644 > > > --- a/Documentation/userspace-api/vduse.rst > > > +++ b/Documentation/userspace-api/vduse.rst > > > @@ -230,4 +230,57 @@ 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. 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_VQ_SETUP) > > > argument to > > > +select the address space of the IOTLB you are querying. The driver could > > > +change the address space of any virtqueue group by using the > > > +VDUSE_SET_VQ_GROUP_ASID VDUSE message type, and the VDUSE instance needs > > > to > > > +reply with VDUSE_REQ_RESULT_OK if it was possible to change it. > > > > Nitpick: Is this better to move this to the part of > > > > "There are now three types of messages introduced by VDUSE framework:" > > > > ? > > > > It makes more sense to add th ASID on top of the simple app example to > me, so developers of simpler apps with no ASID don't need to mess with > it.
That's fine. > But I'm happy to move it if you want. > So Acked-by: Jason Wang <[email protected]> > > > + > > > +Similarly, you can use ioctl(VDUSE_IOTLB_GET_FD2) to obtain the file > > > descriptor > > > +describing an IOVA region of a specific ASID. Example usage: > > > + > > > +.. 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 > > > > > > > Thanks > > > Thanks
