Re: [PATCH v9 11/21] iommufd/device: Move attached device tracking to handle

[Jason Gunthorpe <jgg@nvidia.com>]

On Tue, Mar 18, 2025 at 09:50:12PM +0800, Yi Liu wrote:
> On 2025/3/18 21:26, Jason Gunthorpe wrote:
> > On Tue, Mar 18, 2025 at 09:25:56PM +0800, Yi Liu wrote:
> > > >     	struct iommufd_attach_handle *handle;
> > > > 	struct xarray device_array;
> > > > };
> > > > 
> > > > ?
> > > > 
> > > > I think I'd just accept the additional allocation and not try to make
> > > > handle re-usable. Every unique attach gets a unique handle allocation.
> > > 
> > > If so, we also need to loop the device_array and add the attached devices
> > > to the new device_array of the new handle.
> > 
> > Why? Just don't use the handle for that, as above, the handle is still
> > a pointer that you allocate, and this pasid_enty is another pointer
> > that is allocated once.
> 
> I see. How about making a new structure dedicate for tracking attached hwpt
> and device_array? Like the below. Reusing iommufd_attach_handle structure
> is not mandatory.
> 
> struct iommufd_attach {
>  	struct iommufd_hw_pagetable *hwpt;
> 	struct xarray device_array;
> };

Yeah, something like that would make sense. Then the handle is
allocated uniquely for every attach.

I'd also add info to the kdoc's that handle should not be reused as
part of the API requirement.

Jason