linux-kernel - Re: [PATCH v2 02/22] iommufd: Use iommu_user_domain

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Date: Tue, 4 Jun 2024 13:51:45 -0300
From: Jason Gunthorpe <jgg@...pe.ca>
To: Lu Baolu <baolu.lu@...ux.intel.com>
Cc: Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Kevin Tian <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Kalle Valo <kvalo@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Alex Williamson <alex.williamson@...hat.com>, mst@...hat.com,
	Jason Wang <jasowang@...hat.com>,
	Thierry Reding <thierry.reding@...il.com>,
	Jonathan Hunter <jonathanh@...dia.com>,
	Mikko Perttunen <mperttunen@...dia.com>, iommu@...ts.linux.dev,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 02/22] iommufd: Use iommu_user_domain_alloc()

On Tue, Jun 04, 2024 at 09:51:14AM +0800, Lu Baolu wrote:
> Replace iommu_domain_alloc() with iommu_user_domain_alloc().
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> ---
>  drivers/iommu/iommufd/hw_pagetable.c | 20 +++++---------------
>  1 file changed, 5 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/iommu/iommufd/hw_pagetable.c b/drivers/iommu/iommufd/hw_pagetable.c
> index 33d142f8057d..ada05fccb36a 100644
> --- a/drivers/iommu/iommufd/hw_pagetable.c
> +++ b/drivers/iommu/iommufd/hw_pagetable.c
> @@ -127,21 +127,11 @@ iommufd_hwpt_paging_alloc(struct iommufd_ctx *ictx, struct iommufd_ioas *ioas,
>  	hwpt_paging->ioas = ioas;
>  	hwpt_paging->nest_parent = flags & IOMMU_HWPT_ALLOC_NEST_PARENT;
>  
> -	if (ops->domain_alloc_user) {
> -		hwpt->domain = ops->domain_alloc_user(idev->dev, flags, NULL,
> -						      user_data);
                                                     ^^^^^^^^^^^^

> -		if (IS_ERR(hwpt->domain)) {
> -			rc = PTR_ERR(hwpt->domain);
> -			hwpt->domain = NULL;
> -			goto out_abort;
> -		}
> -		hwpt->domain->owner = ops;
> -	} else {
> -		hwpt->domain = iommu_domain_alloc(idev->dev->bus);
> -		if (!hwpt->domain) {
> -			rc = -ENOMEM;
> -			goto out_abort;
> -		}
> +	hwpt->domain = iommu_user_domain_alloc(idev->dev, flags);
> +	if (IS_ERR(hwpt->domain)) {

Where did the user_data go???

If you are going to wrapper the op function then all the args need to
be provided.

I'm not sure there is value in having vfio and vdpa call this
variation since they won't pass a user_data or flags?

Do you imagine there will ever be a difference between what
domain_alloc_user(dev, 0, NULL, NULL) returns from
domain_alloc_paging(dev) ?

That seems like questionable driver behavior to me.

Jason