RE: [PATCH v2 10/17] iommufd: Reorganize iommufd_device_attach into iommufd_device_change_pt

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> From: Jason Gunthorpe <jgg@xxxxxxxxxx>
> Sent: Wednesday, March 8, 2023 8:36 AM
> 
> @@ -379,52 +388,57 @@ static int
> iommufd_device_auto_get_domain(struct iommufd_device *idev,
> 
>  		if (!iommufd_lock_obj(&hwpt->obj))
>  			continue;
> -		rc = iommufd_device_do_attach(idev, hwpt);
> -		iommufd_put_object(&hwpt->obj);
> -
> -		/*
> -		 * -EINVAL means the domain is incompatible with the device.
> -		 * Other error codes should propagate to userspace as failure.
> -		 * Success means the domain is attached.
> -		 */
> -		if (rc == -EINVAL)
> -			continue;
> +		destroy_hwpt = (*do_attach)(idev, hwpt);
>  		*pt_id = hwpt->obj.id;

only when succeed?

> +		iommufd_put_object(&hwpt->obj);
> +		if (IS_ERR(destroy_hwpt)) {
> +			/*
> +			 * -EINVAL means the domain is incompatible with
> the
> +			 * device. Other error codes should propagate to
> +			 * userspace as failure. Success means the domain is
> +			 * attached.
> +			 */
> +			if (PTR_ERR(destroy_hwpt) == -EINVAL)
> +				continue;
> +			goto out_unlock;
> +		}
>  		goto out_unlock;

two goto's can be merged, if you still want to keep pt_id assignment
in original place.

>  	}
> 
> -	hwpt = iommufd_hw_pagetable_alloc(idev->ictx, ioas, idev, true);
> +	hwpt = iommufd_hw_pagetable_alloc(idev->ictx, ioas, idev,
> +					  immediate_attach);
>  	if (IS_ERR(hwpt)) {
> -		rc = PTR_ERR(hwpt);
> +		destroy_hwpt = ERR_CAST(hwpt);
>  		goto out_unlock;
>  	}
> +
> +	if (!immediate_attach) {
> +		destroy_hwpt = (*do_attach)(idev, hwpt);
> +		if (IS_ERR(destroy_hwpt))
> +			goto out_abort;
> +	} else {
> +		destroy_hwpt = NULL;
> +	}
> +

Above is a bit confusing.

On one hand we have immediate_attach for drivers which must
complete attach before we can add the domain to iopt. From
this angle it should always be set when calling
iommufd_hw_pagetable_alloc() no matter it's attach or replace.

On the other hand we assume *replace* doesn't work with
driver which requires immediate_attach so it's done outside of
iommufd_hw_pagetable_alloc().

I'm unsure any better way of handling this transition phase, but
at least some comment would be useful in this part.




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