Hi Zhangfei,
> -----Original Message-----
> From: Zhangfei Gao <[email protected]>
> Sent: 13 November 2025 11:59
> To: Shameer Kolothum <[email protected]>
> Cc: [email protected]; [email protected];
> [email protected]; [email protected]; Nicolin Chen
> <[email protected]>; Nathan Chen <[email protected]>; Matt Ochs
> <[email protected]>; [email protected];
> [email protected]; Jason Gunthorpe <[email protected]>;
> Krishnakant Jaju <[email protected]>
> Subject: Re: [RFC PATCH 4/4] hw/arm/smmuv3-accel: Read and propagate
> host vIOMMU events
>
> External email: Use caution opening links or attachments
>
>
> Hi, Shameer
>
> 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;
> 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?
> 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?
Thanks,
Shameer
