linux-kernel - Re: [PATCH v3 3/7] iommu/sva: Support allocation of global PASIDs outside SVA

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Date:   Sat, 1 Apr 2023 21:16:39 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Robin Murphy <robin.murphy@....com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org
Cc:     baolu.lu@...ux.intel.com, Will Deacon <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>
Subject: Re: [PATCH v3 3/7] iommu/sva: Support allocation of global PASIDs
 outside SVA

On 2023/4/1 7:11, Jacob Pan wrote:
> Devices that use Intel ENQCMD to submit work must use global PASIDs in
> that the PASID are stored in a per CPU MSR. When such device need to
> submit work for in-kernel DMA with PASID, it must allocate PASIDs from
> the same global number space to avoid conflict.
> 
> This patch moves global PASID allocation APIs from SVA to IOMMU APIs.
> It is expected that device drivers will use the allocated PASIDs to attach
> to appropriate IOMMU domains for use.
> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>   drivers/iommu/iommu-sva.c | 10 ++++------
>   drivers/iommu/iommu.c     | 33 +++++++++++++++++++++++++++++++++
>   include/linux/iommu.h     | 10 ++++++++++
>   3 files changed, 47 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
> index c434b95dc8eb..222544587582 100644
> --- a/drivers/iommu/iommu-sva.c
> +++ b/drivers/iommu/iommu-sva.c
> @@ -9,15 +9,13 @@
>   #include "iommu-sva.h"
>   
>   static DEFINE_MUTEX(iommu_sva_lock);
> -static DEFINE_IDA(iommu_global_pasid_ida);
>   
>   /* Allocate a PASID for the mm within range (inclusive) */
>   static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t max)
>   {
>   	int ret = 0;
>   
> -	if (!pasid_valid(min) || !pasid_valid(max) ||
> -	    min == 0 || max < min)
> +	if (!pasid_valid(min) || !pasid_valid(max) || max < min)
>   		return -EINVAL;
>   
>   	mutex_lock(&iommu_sva_lock);
> @@ -28,8 +26,8 @@ static int iommu_sva_alloc_pasid(struct mm_struct *mm, ioasid_t min, ioasid_t ma
>   		goto out;
>   	}
>   
> -	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
> -	if (ret < min)
> +	ret = iommu_alloc_global_pasid(min, max);
> +	if (!pasid_valid(ret))
>   		goto out;
>   	mm->pasid = ret;
>   	ret = 0;
> @@ -211,5 +209,5 @@ void mm_pasid_drop(struct mm_struct *mm)
>   	if (likely(!pasid_valid(mm->pasid)))
>   		return;
>   
> -	ida_free(&iommu_global_pasid_ida, mm->pasid);
> +	iommu_free_global_pasid(mm->pasid);
>   }
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 10db680acaed..5a8ffdc3063d 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -38,6 +38,7 @@
>   
>   static struct kset *iommu_group_kset;
>   static DEFINE_IDA(iommu_group_ida);
> +static DEFINE_IDA(iommu_global_pasid_ida);
>   
>   static unsigned int iommu_def_domain_type __read_mostly;
>   static bool iommu_dma_strict __read_mostly = IS_ENABLED(CONFIG_IOMMU_DEFAULT_DMA_STRICT);
> @@ -3450,3 +3451,35 @@ struct iommu_domain *iommu_sva_domain_alloc(struct device *dev,
>   
>   	return domain;
>   }
> +
> +/**
> + * @brief
> + *	Reserve a PASID from the SVA global number space.
> + *
> + * @param min starting range, inclusive
> + * @param max ending range, inclusive
> + * @return The reserved PASID on success or IOMMU_PASID_INVALID on failure.
> + */

Nit: the comments here also need to be changed accordingly.

Best regards,
baolu

> +ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max)
> +{
> +	int ret;
> +
> +	if (!pasid_valid(min) || !pasid_valid(max) || max < min)
> +		return IOMMU_PASID_INVALID;
> +
> +	ret = ida_alloc_range(&iommu_global_pasid_ida, min, max, GFP_KERNEL);
> +	if (ret < 0)
> +		return IOMMU_PASID_INVALID;
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iommu_alloc_global_pasid);
> +
> +void iommu_free_global_pasid(ioasid_t pasid)
> +{
> +	if (WARN_ON(!pasid_valid(pasid)))
> +		return;
> +
> +	ida_free(&iommu_global_pasid_ida, pasid);
> +}
> +EXPORT_SYMBOL_GPL(iommu_free_global_pasid);
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 54f535ff9868..f70478a11a5f 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -1187,6 +1187,9 @@ struct iommu_sva *iommu_sva_bind_device(struct device *dev,
>   					struct mm_struct *mm);
>   void iommu_sva_unbind_device(struct iommu_sva *handle);
>   u32 iommu_sva_get_pasid(struct iommu_sva *handle);
> +ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max);
> +void iommu_free_global_pasid(ioasid_t pasid);
> +
>   #else
>   static inline struct iommu_sva *
>   iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
> @@ -1202,6 +1205,13 @@ static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
>   {
>   	return IOMMU_PASID_INVALID;
>   }
> +
> +static inline ioasid_t iommu_alloc_global_pasid(ioasid_t min, ioasid_t max)
> +{
> +	return IOMMU_PASID_INVALID;
> +}
> +
> +static inline void iommu_free_global_pasid(ioasid_t pasid) {}
>   static inline void mm_pasid_init(struct mm_struct *mm) {}
>   static inline void mm_pasid_drop(struct mm_struct *mm) {}
>   #endif /* CONFIG_IOMMU_SVA */