On Fri, Jan 16, 2026 at 10:05 PM Eugenio Pérez <[email protected]> wrote:
>
> Add support for assigning Address Space Identifiers (ASIDs) to each VQ
> group. This enables mapping each group into a distinct memory space.
>
> The vq group to ASID association is protected by a rwlock now. But the
> mutex domain_lock keeps protecting the domains of all ASIDs, as some
> operations like the one related with the bounce buffer size still
> requires to lock all the ASIDs.
>
> Signed-off-by: Eugenio Pérez <[email protected]>
>
> ---
> Future improvements can include performance optimizations on top like
> ore to RCU or thread synchronized atomics, or hardening by tracking ASID
> or ASID hashes on unused bits of the DMA address.
>
> Tested virtio_vdpa by adding manually two threads in vduse_set_status:
> one of them modifies the vq group 0 ASID and the other one map and unmap
> memory continuously. After a while, the two threads stop and the usual
> work continues. Test with version 0, version 1 with the old ioctl, and
> version 1 with the new ioctl.
>
> Tested with vhost_vdpa by migrating a VM while ping on OVS+VDUSE. A few
> workaround were needed in some parts:
> * Do not enable CVQ before data vqs in QEMU, as VDUSE does not forward
> the enable message to the userland device. This will be solved in the
> future.
> * Share the suspended state between all vhost devices in QEMU:
> https://lists.nongnu.org/archive/html/qemu-devel/2025-11/msg02947.html
> * Implement a fake VDUSE suspend vdpa operation callback that always
> returns true in the kernel. DPDK suspend the device at the first
> GET_VRING_BASE.
> * Remove the CVQ blocker in ASID.
>
> The driver vhost_vdpa was also tested with version 0, version 1 with the
> old ioctl, version 1 with the new ioctl but only one ASID, and version 1
> with many ASID.
>
Looks good overall, but I spot a small issue:
int vduse_domain_add_user_bounce_pages(struct vduse_iova_domain *domain,
struct page **pages, int count)
{
struct vduse_bounce_map *map, *head_map;
...
/* Now we don't support partial mapping */
if (count != (domain->bounce_size >> PAGE_SHIFT))
return -EINVAL;
Here we still use domain->bounce_size even if we support multiple as,
this conflicts with the case without userspace memory.
Thanks
