Re: [PATCH 5/6] iommu: init pasid array while doing domain_replace and iopf is active

[Baolu Lu]

On 9/11/24 6:56 PM, Joel Granados wrote:
> On Thu, Sep 05, 2024 at 11:30:05AM +0800, Baolu Lu wrote:
> > On 9/4/24 9:17 PM, Joel Granados via B4 Relay wrote:
> > > From: Joel Granados<j.granados@xxxxxxxxxxx>
> > >
> > > iommu_report_device_fault expects a pasid array to have an
> > > iommu_attach_handle when a fault is detected.
> > The iommu_attach_handle is expected only when an iopf-capable domain is
> > attached to the device or PASID. The iommu_report_device_fault() treats
> > it as a fault when a fault occurs, but no iopf-capable domain is
> > attached.
> >
> > > Add this handle when the
> > > replacing hwpt has a valid iommufd fault object. Remove it when we
> > > release ownership of the group.
> > The iommu_attach_handle is managed by the caller (iommufd here for
> > example). Therefore, before iommu_attach_handle tries to attach a domain
> > to an iopf-capable device or pasid, it should allocate the handle and
> > pass it to the domain attachment interfaces.
> What do you mean here?
> 1. Do you want to move the iommufd_init_pasid_array call up to
> iommufd_hwpt_replace_device?
> 2. Do you want to move it further up to iommufd_device_do_replace?

I'm having trouble understanding the need for iommu_init_pasid_array()
in the core.

> Note that all this implemented on a call to replace HWPT. So a
> non-iopf-capable VFIO_DEVICE_ATTACH_IOMMUFD_PT ioctl has already been
> completed before the one that calls iommufd_device_do_replace.
>
> > Conversely, the handle can
> > only be freed after the domain is detached.
> Do you have a function in specific where you would put the free handle
> logic?

drivers/iommu/iommufd/fault.c

void iommufd_fault_domain_detach_dev(struct iommufd_hw_pagetable *hwpt,
                                     struct iommufd_device *idev)
{
        struct iommufd_attach_handle *handle;

        handle = iommufd_device_get_attach_handle(idev);
        iommu_detach_group_handle(hwpt->domain, idev->igroup->group);
        iommufd_auto_response_faults(hwpt, handle);
        iommufd_fault_iopf_disable(idev);
        kfree(handle);
}

Thanks,
baolu