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Date:   Tue, 29 Mar 2022 14:38:48 -0700
From:   Jacob Pan <jacob.jun.pan@intel.com>
To:     Lu Baolu <baolu.lu@linux.intel.com>
Cc:     Joerg Roedel <joro@8bytes.org>, Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@infradead.org>,
        Kevin Tian <kevin.tian@intel.com>,
        Ashok Raj <ashok.raj@intel.com>, Will Deacon <will@kernel.org>,
        Robin Murphy <robin.murphy@arm.com>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org,
        jacob.jun.pan@intel.com
Subject: Re: [PATCH RFC v2 03/11] iommu/sva: Add iommu_domain type for SVA
Message-ID: <20220329143848.2e763727@jacob-builder>
In-Reply-To: <20220329053800.3049561-4-baolu.lu@linux.intel.com>
References: <20220329053800.3049561-1-baolu.lu@linux.intel.com>
        <20220329053800.3049561-4-baolu.lu@linux.intel.com>
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Hi BaoLu,

On Tue, 29 Mar 2022 13:37:52 +0800, Lu Baolu <baolu.lu@linux.intel.com>
wrote:

> Add a new iommu domain type IOMMU_DOMAIN_SVA to represent an I/O page
> table which is shared from CPU host VA. Add some helpers to get and
> put an SVA domain and implement SVA domain life cycle management.
> 
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
>  include/linux/iommu.h         |  7 +++
>  drivers/iommu/iommu-sva-lib.h | 10 ++++
>  drivers/iommu/iommu-sva-lib.c | 89 +++++++++++++++++++++++++++++++++++
>  3 files changed, 106 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 36f43af0af53..29c4c2edd706 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -42,6 +42,7 @@ struct notifier_block;
>  struct iommu_sva;
>  struct iommu_fault_event;
>  struct iommu_dma_cookie;
> +struct iommu_sva_cookie;
>  
>  /* iommu fault flags */
>  #define IOMMU_FAULT_READ	0x0
> @@ -64,6 +65,9 @@ struct iommu_domain_geometry {
>  #define __IOMMU_DOMAIN_PT	(1U << 2)  /* Domain is identity mapped
>   */ #define __IOMMU_DOMAIN_DMA_FQ	(1U << 3)  /* DMA-API uses
> flush queue    */ 
> +#define __IOMMU_DOMAIN_SHARED	(1U << 4)  /* Page table shared
> from CPU  */ +#define __IOMMU_DOMAIN_HOST_VA	(1U << 5)  /* Host
> CPU virtual address */ +
>  /*
>   * This are the possible domain-types
>   *
> @@ -86,6 +90,8 @@ struct iommu_domain_geometry {
>  #define IOMMU_DOMAIN_DMA_FQ	(__IOMMU_DOMAIN_PAGING |	\
>  				 __IOMMU_DOMAIN_DMA_API |	\
>  				 __IOMMU_DOMAIN_DMA_FQ)
> +#define IOMMU_DOMAIN_SVA	(__IOMMU_DOMAIN_SHARED |	\
> +				 __IOMMU_DOMAIN_HOST_VA)
>  
>  struct iommu_domain {
>  	unsigned type;
> @@ -95,6 +101,7 @@ struct iommu_domain {
>  	void *handler_token;
>  	struct iommu_domain_geometry geometry;
>  	struct iommu_dma_cookie *iova_cookie;
> +	struct iommu_sva_cookie *sva_cookie;
>  };
>  
>  static inline bool iommu_is_dma_domain(struct iommu_domain *domain)
> diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
> index 8909ea1094e3..1a71218b07f5 100644
> --- a/drivers/iommu/iommu-sva-lib.h
> +++ b/drivers/iommu/iommu-sva-lib.h
> @@ -10,6 +10,7 @@
>  
>  int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t
> max); struct mm_struct *iommu_sva_find(ioasid_t pasid);
> +struct mm_struct *iommu_sva_domain_mm(struct iommu_domain *domain);
>  
>  /* I/O Page fault */
>  struct device;
> @@ -26,6 +27,8 @@ int iopf_queue_flush_dev(struct device *dev);
>  struct iopf_queue *iopf_queue_alloc(const char *name);
>  void iopf_queue_free(struct iopf_queue *queue);
>  int iopf_queue_discard_partial(struct iopf_queue *queue);
> +bool iommu_sva_domain_get_user(struct iommu_domain *domain);
> +void iommu_sva_domain_put_user(struct iommu_domain *domain);
>  
>  #else /* CONFIG_IOMMU_SVA */
>  static inline int iommu_queue_iopf(struct iommu_fault *fault, void
> *cookie) @@ -63,5 +66,12 @@ static inline int
> iopf_queue_discard_partial(struct iopf_queue *queue) {
>  	return -ENODEV;
>  }
> +
> +static inline bool iommu_sva_domain_get_user(struct iommu_domain *domain)
> +{
> +	return false;
> +}
> +
> +static inline void iommu_sva_domain_put_user(struct iommu_domain
> *domain) { } #endif /* CONFIG_IOMMU_SVA */
>  #endif /* _IOMMU_SVA_LIB_H */
> diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
> index 106506143896..78820be23f15 100644
> --- a/drivers/iommu/iommu-sva-lib.c
> +++ b/drivers/iommu/iommu-sva-lib.c
> @@ -3,12 +3,21 @@
>   * Helpers for IOMMU drivers implementing SVA
>   */
>  #include <linux/mutex.h>
> +#include <linux/iommu.h>
> +#include <linux/slab.h>
>  #include <linux/sched/mm.h>
>  
>  #include "iommu-sva-lib.h"
>  
>  static DEFINE_MUTEX(iommu_sva_lock);
>  static DECLARE_IOASID_SET(iommu_sva_pasid);
> +static DEFINE_XARRAY_ALLOC(sva_domain_array);
> +
> +struct iommu_sva_cookie {
> +	struct mm_struct *mm;
> +	ioasid_t pasid;
> +	refcount_t users;
> +};
>  
>  /**
>   * iommu_sva_alloc_pasid - Allocate a PASID for the mm
> @@ -69,3 +78,83 @@ struct mm_struct *iommu_sva_find(ioasid_t pasid)
>  	return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
>  }
>  EXPORT_SYMBOL_GPL(iommu_sva_find);
> +
> +static struct iommu_domain *
> +iommu_sva_alloc_domain(struct device *dev, struct mm_struct *mm)
> +{
> +	struct bus_type *bus = dev->bus;
> +	struct iommu_sva_cookie *cookie;
> +	struct iommu_domain *domain;
> +	void *curr;
> +
> +	if (!bus || !bus->iommu_ops)
> +		return NULL;
> +
> +	cookie = kzalloc(sizeof(*cookie), GFP_KERNEL);
> +	if (!cookie)
> +		return NULL;
> +
> +	domain = bus->iommu_ops->domain_alloc(IOMMU_DOMAIN_SVA);
> +	if (!domain)
> +		goto err_domain_alloc;
> +
> +	cookie->mm = mm;
> +	cookie->pasid = mm->pasid;
How do you manage the mm life cycle? do you require caller take mm reference?
Or this should be limited to the current mm?

> +	refcount_set(&cookie->users, 1);
> +	domain->type = IOMMU_DOMAIN_SVA;
> +	domain->sva_cookie = cookie;
> +	curr = xa_store(&sva_domain_array, mm->pasid, domain,
> GFP_KERNEL);
> +	if (xa_err(curr))
> +		goto err_xa_store;
> +
> +	return domain;
> +err_xa_store:
> +	domain->ops->free(domain);
> +err_domain_alloc:
> +	kfree(cookie);
> +	return NULL;
> +}
> +
> +static void iommu_sva_free_domain(struct iommu_domain *domain)
> +{
> +	xa_erase(&sva_domain_array, domain->sva_cookie->pasid);
> +	kfree(domain->sva_cookie);
> +	domain->ops->free(domain);
> +}
> +
> +bool iommu_sva_domain_get_user(struct iommu_domain *domain)
> +{
> +	struct iommu_sva_cookie *cookie = domain->sva_cookie;
> +
> +	return refcount_inc_not_zero(&cookie->users);
> +}
> +
> +void iommu_sva_domain_put_user(struct iommu_domain *domain)
> +{
> +	struct iommu_sva_cookie *cookie = domain->sva_cookie;
> +
> +	if (refcount_dec_and_test(&cookie->users))
> +		iommu_sva_free_domain(domain);
> +}
> +
> +static __maybe_unused struct iommu_domain *
> +iommu_sva_get_domain(struct device *dev, struct mm_struct *mm)
> +{
> +	struct iommu_domain *domain;
> +	ioasid_t pasid = mm->pasid;
> +
> +	if (pasid == INVALID_IOASID)
> +		return NULL;
> +
> +	domain = xa_load(&sva_domain_array, pasid);
> +	if (!domain)
> +		return iommu_sva_alloc_domain(dev, mm);
> +	iommu_sva_domain_get_user(domain);
> +
> +	return domain;
> +}
> +
> +struct mm_struct *iommu_sva_domain_mm(struct iommu_domain *domain)
> +{
> +	return domain->sva_cookie->mm;
> +}


Thanks,

Jacob