Re: [PATCH 09/14] iommufd: Add iommufd_device_replace()

[Jason Gunthorpe <jgg@nvidia.com>]

On Sun, Feb 26, 2023 at 11:13:16AM +0800, Baolu Lu wrote:
> On 2/25/23 8:27 AM, Jason Gunthorpe wrote:
> > +/**
> > + * iommufd_device_attach - Connect a device to an iommu_domain
> > + * @idev: device to attach
> > + * @pt_id: Input a IOMMUFD_OBJ_IOAS, or IOMMUFD_OBJ_HW_PAGETABLE
> > + *         Output the IOMMUFD_OBJ_HW_PAGETABLE ID
> 
> "Output the hwpt ID" only happens when the caller input an IOAS object
> and an auto domain was selected or created for the device.
> 
> Do I understand it right?

Technically it always outputs the hwpt, if a hwpt is in put then the
same hwpt is output.

> >   EXPORT_SYMBOL_NS_GPL(iommufd_device_attach, IOMMUFD);
> > +/**
> > + * iommufd_device_replace - Change the device's iommu_domain
> > + * @idev: device to change
> > + * @pt_id: Input a IOMMUFD_OBJ_IOAS, or IOMMUFD_OBJ_HW_PAGETABLE
> > + *         Output the IOMMUFD_OBJ_HW_PAGETABLE ID
> 
> If my above understanding is correct, then replace will never output a
> hwpt id as it only happens after a successful attach.

Replace calls iommufd_device_auto_get_domain() which always sets pt_id
on success?

If a HWPT was passed in then it just leaves it unchanged which is also
correct.

Jason