Re: [PATCH RFC 10/12] iommufd: Add kAPI toward external drivers

[Jason Gunthorpe via iommu <iommu@lists.linux-foundation.org>]

On Thu, May 19, 2022 at 05:45:06PM +0800, Yi Liu wrote:
> Hi Jason,
> 
> On 2022/3/19 01:27, 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
> > + * @flags: Optional flags
> > + *
> > + * This connects the device to an iommu_domain, either automatically or manually
> > + * selected. Once this completes the device could do DMA.
> > + *
> > + * The caller should return the resulting pt_id back to userspace.
> > + * This function is undone by calling iommufd_device_detach().
> > + */
> > +int iommufd_device_attach(struct iommufd_device *idev, u32 *pt_id,
> > +			  unsigned int flags)
> > +{

> Just double check here.
> This API doesn't prevent caller from calling this API multiple times with
> the same @idev and @pt_id. right? Note that idev has only one device_item
> list head. If caller does do multiple callings, then there should be
> problem. right? If so, this API assumes caller should take care of it and
> not do such bad function call. Is this the design here?

Yes, caller must ensure strict pairing, we don't have an assertion to
check it.

Jason
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu