linux-kernel - Re: [PATCH v5 02/12] iommu: Add pasid_bits field in struct dev

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Date:   Tue, 3 May 2022 19:02:22 +0100
From:   Jean-Philippe Brucker <jean-philippe@...aro.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Joerg Roedel <joro@...tes.org>, Jason Gunthorpe <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 02/12] iommu: Add pasid_bits field in struct dev_iommu

On Mon, May 02, 2022 at 09:48:32AM +0800, Lu Baolu wrote:
> Use this field to save the pasid/ssid bits that a device is able to
> support with its IOMMU hardware. It is a generic attribute of a device
> and lifting it into the per-device dev_iommu struct makes it possible
> to allocate a PASID for device without calls into the IOMMU drivers.
> Any iommu driver which suports PASID related features should set this
> field before features are enabled on the devices.
> 
> For initialization of this field in the VT-d driver, the
> info->pasid_supported is only set for PCI devices. So the status is
> that non-PCI SVA hasn't been supported yet. Setting this field only for
> PCI devices has no functional change.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>

Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>

> ---
>  include/linux/iommu.h                       | 1 +
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 2 ++
>  drivers/iommu/intel/iommu.c                 | 5 ++++-
>  3 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 5e1afe169549..b8ffaf2cb1d0 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -373,6 +373,7 @@ struct dev_iommu {
>  	struct iommu_fwspec		*fwspec;
>  	struct iommu_device		*iommu_dev;
>  	void				*priv;
> +	unsigned int			pasid_bits;
>  };
>  
>  int iommu_device_register(struct iommu_device *iommu,
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 627a3ed5ee8f..afc63fce6107 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2681,6 +2681,8 @@ static struct iommu_device *arm_smmu_probe_device(struct device *dev)
>  	    smmu->features & ARM_SMMU_FEAT_STALL_FORCE)
>  		master->stall_enabled = true;
>  
> +	dev->iommu->pasid_bits = master->ssid_bits;
> +
>  	return &smmu->iommu;
>  
>  err_free_master:
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index cf43e8f9091b..170eb777d57b 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -4611,8 +4611,11 @@ static struct iommu_device *intel_iommu_probe_device(struct device *dev)
>  			if (pasid_supported(iommu)) {
>  				int features = pci_pasid_features(pdev);
>  
> -				if (features >= 0)
> +				if (features >= 0) {
>  					info->pasid_supported = features | 1;
> +					dev->iommu->pasid_bits =
> +						fls(pci_max_pasids(pdev)) - 1;
> +				}
>  			}
>  
>  			if (info->ats_supported && ecap_prs(iommu->ecap) &&
> -- 
> 2.25.1
>