linux-kernel - RE: [PATCH v7 10/28] iommufd/access: Bypass access->ops->unmap for internal use

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Message-ID: <BN9PR11MB5276F03CF1E97173E711A5288C40A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date: Wed, 2 Jul 2025 09:45:26 +0000
From: "Tian, Kevin" <kevin.tian@...el.com>
To: Nicolin Chen <nicolinc@...dia.com>, "jgg@...dia.com" <jgg@...dia.com>,
	"corbet@....net" <corbet@....net>, "will@...nel.org" <will@...nel.org>
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Subject: RE: [PATCH v7 10/28] iommufd/access: Bypass access->ops->unmap for
 internal use

> From: Nicolin Chen <nicolinc@...dia.com>
> Sent: Friday, June 27, 2025 3:35 AM
> 
> +int iommufd_access_notify_unmap(struct io_pagetable *iopt, unsigned long
> iova,
> +				unsigned long length)
>  {
>  	struct iommufd_ioas *ioas =
>  		container_of(iopt, struct iommufd_ioas, iopt);
>  	struct iommufd_access *access;
>  	unsigned long index;
> +	int ret = 0;
> 
>  	xa_lock(&ioas->iopt.access_list);
> +	/* Bypass any unmap if there is an internal access */
> +	xa_for_each(&ioas->iopt.access_list, index, access) {
> +		if (iommufd_access_is_internal(access)) {
> +			ret = -EBUSY;
> +			goto unlock;
> +		}
> +	}
> +

hmm all those checks are per iopt. Could do one-off check in
iopt_unmap_iova_range() and store the result in a local flag.

Then use that flag to decide whether to return -EBUSY if
area->num_accesses is true in the loop.

Reviewed-by: Kevin Tian <kevin.tian@...el.com>