linux-kernel - Re: [PATCH v4 2/6] iommu: Add a helper to do PASID lookup from domain

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Message-ID: <41c717e3-2965-67ac-9140-72f4b071cd9a@linux.intel.com>
Date:   Thu, 19 May 2022 14:41:06 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        iommu@...ts.linux-foundation.org,
        LKML <linux-kernel@...r.kernel.org>, dmaengine@...r.kernel.org,
        Joerg Roedel <joro@...tes.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>, vkoul@...nel.org,
        robin.murphy@....com, will@...nel.org
Cc:     baolu.lu@...ux.intel.com, Yi Liu <yi.l.liu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>,
        Raj Ashok <ashok.raj@...el.com>,
        Eric Auger <eric.auger@...hat.com>
Subject: Re: [PATCH v4 2/6] iommu: Add a helper to do PASID lookup from domain

On 2022/5/19 02:21, Jacob Pan wrote:
> IOMMU group maintains a PASID array which stores the associated IOMMU
> domains. This patch introduces a helper function to do domain to PASID
> look up. It will be used by TLB flush and device-PASID attach verification.

Do you really need this?

The IOMMU driver has maintained a device tracking list for each domain.
It has been used for cache invalidation when unmap() is called against
dma domain.

Best regards,
baolu

> 
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>   drivers/iommu/iommu.c | 22 ++++++++++++++++++++++
>   include/linux/iommu.h |  6 +++++-
>   2 files changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 00d0262a1fe9..22f44833db64 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -3199,3 +3199,25 @@ struct iommu_domain *iommu_get_domain_for_iopf(struct device *dev,
>   
>   	return domain;
>   }
> +
> +ioasid_t iommu_get_pasid_from_domain(struct device *dev, struct iommu_domain *domain)
> +{
> +	struct iommu_domain *tdomain;
> +	struct iommu_group *group;
> +	unsigned long index;
> +	ioasid_t pasid = INVALID_IOASID;
> +
> +	group = iommu_group_get(dev);
> +	if (!group)
> +		return pasid;
> +
> +	xa_for_each(&group->pasid_array, index, tdomain) {
> +		if (domain == tdomain) {
> +			pasid = index;
> +			break;
> +		}
> +	}
> +	iommu_group_put(group);
> +
> +	return pasid;
> +}
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 36ad007084cc..c0440a4be699 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -694,7 +694,7 @@ void iommu_detach_device_pasid(struct iommu_domain *domain,
>   			       struct device *dev, ioasid_t pasid);
>   struct iommu_domain *
>   iommu_get_domain_for_iopf(struct device *dev, ioasid_t pasid);
> -
> +ioasid_t iommu_get_pasid_from_domain(struct device *dev, struct iommu_domain *domain);
>   #else /* CONFIG_IOMMU_API */
>   
>   struct iommu_ops {};
> @@ -1070,6 +1070,10 @@ iommu_get_domain_for_iopf(struct device *dev, ioasid_t pasid)
>   {
>   	return NULL;
>   }
> +static ioasid_t iommu_get_pasid_from_domain(struct device *dev, struct iommu_domain *domain)
> +{
> +	return INVALID_IOASID;
> +}
>   #endif /* CONFIG_IOMMU_API */
>   
>   #ifdef CONFIG_IOMMU_SVA