On Thu, Nov 13, 2025 at 05:07:50AM -0800, Shameer Kolothum wrote: > > On Wed, 5 Nov 2025 at 23:49, Shameer Kolothum > > <[email protected]> wrote: > > > > > > Install an event handler on the vEVENTQ fd to read and propagate host > > > generated vIOMMU events to the guest. > > > > > > The handler runs in QEMU’s main loop, using a non-blocking fd registered > > > via qemu_set_fd_handler(). > > > > > > Signed-off-by: Shameer Kolothum <[email protected]> > > > > Still don't understand how to use this vevent. > > Is it to replace the fault queue (IOMMU_FAULT_QUEUE_ALLOC)? > > No. IIUC, IOMMU_FAULT_QUEUE_ALLOC is to handle I/O page faults > for any HWPT capable of handling page faults/response. The QEMU > SMMUv3 still don't support page fault handling. > > The VEVENTQ, on the other hand, provides a way to report any > other s1 events to Guest. > > See how events are reported in arm_smmu_handle_event(): > > if (event->stall) > ret = iommu_report_device_fault(master->dev, &fault_evt); //Page faults > else if (master->vmaster && !event->s2) > ret = arm_vmaster_report_event(master->vmaster, evt); //This series > handles this case. > else > ret = -EOPNOTSUPP;
Yes. We can say that FAULT_QUEUE is exclusively for PRI while the vEVENTQ is for other types of HW events (or IRQs) related to the guest stage-1. They can be used together. > > And only find read, no write, only receive events but no response > > (from guest kernel)? > > Yes. And I am not sure what the long term plan is. We can still use > IOMMU_FAULT_QUEUE_ALLOC for page fault handling or extend this > VEVENTQ to have write() support for responses > > To me, from an implementation perspective, both this FAULT and > VEVENTQ look almost similar. > > @Nicolin, any idea what's plan for page fault handling? No. I think PRI should be done via FAULT_QUEUE. > > By the way, can we use vevent in user space application? not in qemu > > environment. > > I didn't get that. Qemu is userspace. Or you meant just to receive any events > from host SMMUv3 in user spacel? If user space application follows the iommufd uAPI like QEMU does, it can. I am not sure about the use case though. Nicolin
