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

[Yi Liu <yi.l.liu@intel.com>]

On 2025/3/18 20:34, Jason Gunthorpe wrote:
> On Thu, Mar 13, 2025 at 05:35:22AM -0700, Yi Liu wrote:
>> By tracking both attached hwpt and devices, iommufd_attach_handle is
>> prepared to be used as attach object. This prepares for adding per-PASID
>> attachment by using handle.
> 
> So this is the patch that really requires re-using the handle..
> 
> The issue you are trying to solve is to avoid a second memory
> allocation when storing the PASID in the xarray?

and another is to avoid copying all the tracked devices in the device_array
in the replace path.

> struct xarray_pasid_entry {
>    	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.

-- 
Regards,
Yi Liu