linux-kernel - Re: [PATCH v3 01/21] iommu: Add iommu_paging_domain

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Date: Thu, 27 Jun 2024 12:40:49 +0530
From: Vasant Hegde <vasant.hegde@....com>
To: Lu Baolu <baolu.lu@...ux.intel.com>, Joerg Roedel <joro@...tes.org>,
 Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
 Jason Gunthorpe <jgg@...pe.ca>, Kevin Tian <kevin.tian@...el.com>
Cc: 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>,
 Jeff Johnson <quic_jjohnson@...cinc.com>, ath10k@...ts.infradead.org,
 ath11k@...ts.infradead.org, iommu@...ts.linux.dev,
 dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/21] iommu: Add iommu_paging_domain_alloc() interface

On 6/10/2024 2:25 PM, Lu Baolu wrote:
> Commit <17de3f5fdd35> ("iommu: Retire bus ops") removes iommu ops from
> bus. The iommu subsystem no longer relies on bus for operations. So the
> bus parameter in iommu_domain_alloc() is no longer relevant.
> 
> Add a new interface named iommu_paging_domain_alloc(), which explicitly
> indicates the allocation of a paging domain for DMA managed by a kernel
> driver. The new interface takes a device pointer as its parameter, that
> better aligns with the current iommu subsystem.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Reviewed-by: Vasant Hegde <vasant.hegde@....com>

-Vasant

> ---
>  include/linux/iommu.h |  6 ++++++
>  drivers/iommu/iommu.c | 20 ++++++++++++++++++++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 7bc8dff7cf6d..46f1348f1f0a 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -780,6 +780,7 @@ extern bool iommu_present(const struct bus_type *bus);
>  extern bool device_iommu_capable(struct device *dev, enum iommu_cap cap);
>  extern bool iommu_group_has_isolated_msi(struct iommu_group *group);
>  extern struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus);
> +struct iommu_domain *iommu_paging_domain_alloc(struct device *dev);
>  extern void iommu_domain_free(struct iommu_domain *domain);
>  extern int iommu_attach_device(struct iommu_domain *domain,
>  			       struct device *dev);
> @@ -1086,6 +1087,11 @@ static inline struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus
>  	return NULL;
>  }
>  
> +static inline struct iommu_domain *iommu_paging_domain_alloc(struct device *dev)
> +{
> +	return ERR_PTR(-ENODEV);
> +}
> +
>  static inline void iommu_domain_free(struct iommu_domain *domain)
>  {
>  }
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 9df7cc75c1bc..e03c71a34347 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -2016,6 +2016,10 @@ static int __iommu_domain_alloc_dev(struct device *dev, void *data)
>  	return 0;
>  }
>  
> +/*
> + * The iommu ops in bus has been retired. Do not use this interface in
> + * new drivers.
> + */
>  struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
>  {
>  	const struct iommu_ops *ops = NULL;
> @@ -2032,6 +2036,22 @@ struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
>  }
>  EXPORT_SYMBOL_GPL(iommu_domain_alloc);
>  
> +/**
> + * iommu_paging_domain_alloc() - Allocate a paging domain
> + * @dev: device for which the domain is allocated
> + *
> + * Allocate a paging domain which will be managed by a kernel driver. Return
> + * allocated domain if successful, or a ERR pointer for failure.
> + */
> +struct iommu_domain *iommu_paging_domain_alloc(struct device *dev)
> +{
> +	if (!dev_has_iommu(dev))
> +		return ERR_PTR(-ENODEV);
> +
> +	return __iommu_domain_alloc(dev_iommu_ops(dev), dev, IOMMU_DOMAIN_UNMANAGED);
> +}
> +EXPORT_SYMBOL_GPL(iommu_paging_domain_alloc);
> +
>  void iommu_domain_free(struct iommu_domain *domain)
>  {
>  	if (domain->type == IOMMU_DOMAIN_SVA)