On Fri, Jan 10, 2025 at 07:06:49AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@xxxxxxxxxx>
> > Sent: Wednesday, January 8, 2025 1:10 AM
> > +
> > +int iommufd_veventq_alloc(struct iommufd_ucmd *ucmd)
> > +{
> > + struct iommu_veventq_alloc *cmd = ucmd->cmd;
> > + struct iommufd_veventq *veventq;
> > + struct iommufd_viommu *viommu;
> > + int fdno;
> > + int rc;
> > +
> > + if (cmd->flags || cmd->type == IOMMU_VEVENTQ_TYPE_DEFAULT)
> > + return -EOPNOTSUPP;
> > +
> > + viommu = iommufd_get_viommu(ucmd, cmd->viommu_id);
> > + if (IS_ERR(viommu))
> > + return PTR_ERR(viommu);
> > +
> > + if (!viommu->ops || !viommu->ops->supports_veventq ||
> > + !viommu->ops->supports_veventq(cmd->type))
> > + return -EOPNOTSUPP;
> > +
>
> I'm not sure about the necessity of above check. The event queue
> is just a software struct with a user-specified format for the iommu
> driver to report viommu event. The struct itself is not constrained
> by the hardware capability, though I'm not sure a real usage in
> which a smmu driver wants to report a vtd event. But legitimately
> an user can create any type of event queues which might just be
> never used.
Allowing a random type that a driver will never use for reporting
doesn't sound to make a lot of sense to me...
That being said, yea..I guess we could drop the limit here, since
it isn't going to break anything?
> It sounds clearer to do the check when IOPF cap is actually enabled
> on a device contained in the viommu. At that point check whether
> a required type eventqueue has been created. If not then fail the
> iopf enabling.
Hmm, isn't IOPF a different channel?
And a vEVENTQ is per vIOMMU, not necessarily per vDEVICE/device..
> Then it reveals probably another todo in this series. Seems you still
> let the smmu driver statically enable iopf when probing the device.
> Sounds like iommufd_viommu_alloc_hwpt_nested() may accept
> IOMMU_HWPT_FAULT_ID_VALID to refer to a event queue and
> later dynamically enable/disable iopf when attaching a device to the
> hwpt and check the event queue type there. Just like how the fault
> object is handled.
You've lost me here :-/
Thanks
Nicolin
