linux-kernel - Re: [PATCH v6 05/10] iommufd: Derive iommufd_hwpt_paging from iommufd_hw

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Date:   Tue, 24 Oct 2023 13:31:30 -0300
From:   Jason Gunthorpe <jgg@...dia.com>
To:     Yi Liu <yi.l.liu@...el.com>
Cc:     joro@...tes.org, alex.williamson@...hat.com, kevin.tian@...el.com,
        robin.murphy@....com, baolu.lu@...ux.intel.com, cohuck@...hat.com,
        eric.auger@...hat.com, nicolinc@...dia.com, kvm@...r.kernel.org,
        mjrosato@...ux.ibm.com, chao.p.peng@...ux.intel.com,
        yi.y.sun@...ux.intel.com, peterx@...hat.com, jasowang@...hat.com,
        shameerali.kolothum.thodi@...wei.com, lulu@...hat.com,
        suravee.suthikulpanit@....com, iommu@...ts.linux.dev,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        zhenzhong.duan@...el.com, joao.m.martins@...cle.com
Subject: Re: [PATCH v6 05/10] iommufd: Derive iommufd_hwpt_paging from
 iommufd_hw_pagetable

On Tue, Oct 24, 2023 at 08:06:04AM -0700, Yi Liu wrote:

>  static int iommufd_group_do_replace_paging(struct iommufd_group *igroup,
> -					   struct iommufd_hw_pagetable *hwpt)
> +					   struct iommufd_hwpt_paging *hwpt_paging)
>  {
>  	struct iommufd_hw_pagetable *old_hwpt = igroup->hwpt;
>  	struct iommufd_device *cur;
> @@ -441,22 +447,23 @@ static int iommufd_group_do_replace_paging(struct iommufd_group *igroup,
>  
>  	lockdep_assert_held(&igroup->lock);
>  
> -	if (hwpt_is_paging(old_hwpt) && hwpt->ioas != old_hwpt->ioas) {
> +	if (hwpt_is_paging(old_hwpt) &&
> +	    hwpt_paging->ioas != to_hwpt_paging(old_hwpt)->ioas) {
>  		list_for_each_entry(cur, &igroup->device_list, group_item) {
>  			rc = iopt_table_enforce_dev_resv_regions(
> -				&hwpt->ioas->iopt, cur->dev, NULL);
> +				&hwpt_paging->ioas->iopt, cur->dev, NULL);
>  			if (rc)
>  				goto err_unresv;
>  		}
>  	}
>  
> -	rc = iommufd_group_setup_msi(igroup, hwpt);
> +	rc = iommufd_group_setup_msi(igroup, hwpt_paging);
>  	if (rc)
>  		goto err_unresv;
>  	return 0;
>  
>  err_unresv:
> -	iommufd_group_remove_reserved_iova(igroup, hwpt);
> +	iommufd_group_remove_reserved_iova(igroup, hwpt_paging);
>  	return rc;
>  }
>  
> @@ -482,7 +489,8 @@ iommufd_device_do_replace(struct iommufd_device *idev,
>  	}
>  
>  	if (hwpt_is_paging(hwpt)) {
> -		rc = iommufd_group_do_replace_paging(igroup, hwpt);
> +		rc = iommufd_group_do_replace_paging(igroup,
> +						     to_hwpt_paging(hwpt));
>  		if (rc)
>  			goto err_unlock;
>  	}
> @@ -493,8 +501,10 @@ iommufd_device_do_replace(struct iommufd_device *idev,
>  
>  	old_hwpt = igroup->hwpt;
>  	if (hwpt_is_paging(old_hwpt) &&
> -	    (!hwpt_is_paging(hwpt) || hwpt->ioas != old_hwpt->ioas))
> -		iommufd_group_remove_reserved_iova(igroup, old_hwpt);
> +	    (!hwpt_is_paging(hwpt) ||
> +	     to_hwpt_paging(hwpt)->ioas != to_hwpt_paging(old_hwpt)->ioas))
> +		iommufd_group_remove_reserved_iova(igroup,
> +						   to_hwpt_paging(old_hwpt));
>  
>  	igroup->hwpt = hwpt;
>  
> @@ -513,7 +523,8 @@ iommufd_device_do_replace(struct iommufd_device *idev,
>  	return old_hwpt;
>  err_unresv:
>  	if (hwpt_is_paging(hwpt))
> -		iommufd_group_remove_reserved_iova(igroup, hwpt);
> +		iommufd_group_remove_reserved_iova(igroup,
> +						   to_hwpt_paging(old_hwpt));

This gets a compiler warning:

../drivers/iommu/iommufd/device.c:527:25: warning: variable 'old_hwpt' is uninitialized when used here [-Wuninitialized]
                                                   to_hwpt_paging(old_hwpt));
                                                                  ^~~~~~~~
../drivers/iommu/iommufd/device.c:475:39: note: initialize the variable 'old_hwpt' to silence this warning
        struct iommufd_hw_pagetable *old_hwpt;
                                             ^
                                              = NULL

I fixed it with:

--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -488,6 +488,7 @@ iommufd_device_do_replace(struct iommufd_device *idev,
                return NULL;
        }
 
+       old_hwpt = igroup->hwpt;
        if (hwpt_is_paging(hwpt)) {
                rc = iommufd_group_do_replace_paging(igroup,
                                                     to_hwpt_paging(hwpt));
@@ -499,7 +500,6 @@ iommufd_device_do_replace(struct iommufd_device *idev,
        if (rc)
                goto err_unresv;
 
-       old_hwpt = igroup->hwpt;
        if (hwpt_is_paging(old_hwpt) &&
            (!hwpt_is_paging(hwpt) ||
             to_hwpt_paging(hwpt)->ioas != to_hwpt_paging(old_hwpt)->ioas))

Jason