linux-kernel - RE: [PATCH v7 01/10] iommu: Add pasids field in struct iommu

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Date:   Tue, 24 May 2022 09:24:41 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        "Jason Gunthorpe" <jgg@...dia.com>,
        Christoph Hellwig <hch@...radead.org>,
        "Raj, Ashok" <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.com>,
        "Jiang, Dave" <dave.jiang@...el.com>, Vinod Koul <vkoul@...nel.org>
CC:     Eric Auger <eric.auger@...hat.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "Pan, Jacob jun" <jacob.jun.pan@...el.com>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Jean-Philippe Brucker" <jean-philippe@...aro.org>
Subject: RE: [PATCH v7 01/10] iommu: Add pasids field in struct iommu_device

> From: Lu Baolu <baolu.lu@...ux.intel.com>
> Sent: Thursday, May 19, 2022 3:21 PM
> 
> Use this field to keep the number of supported PASIDs that an IOMMU
> hardware is able to support. This is a generic attribute of an IOMMU
> and lifting it into the per-IOMMU device structure 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 enabling them on the devices.
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Reviewed-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
> ---
>  include/linux/iommu.h                       | 2 ++
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 1 +
>  drivers/iommu/intel/dmar.c                  | 4 ++++
>  3 files changed, 7 insertions(+)
> 
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 5e1afe169549..da423e87f248 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -318,12 +318,14 @@ struct iommu_domain_ops {
>   * @list: Used by the iommu-core to keep a list of registered iommus
>   * @ops: iommu-ops for talking to this iommu
>   * @dev: struct device for sysfs handling
> + * @pasids: number of supported PASIDs
>   */
>  struct iommu_device {
>  	struct list_head list;
>  	const struct iommu_ops *ops;
>  	struct fwnode_handle *fwnode;
>  	struct device *dev;
> +	u32 pasids;

max_pasid or nr_pasids?

>  };
> 
>  /**
> 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 88817a3376ef..6e2cd082c670 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -3546,6 +3546,7 @@ static int arm_smmu_device_hw_probe(struct
> arm_smmu_device *smmu)
>  	/* SID/SSID sizes */
>  	smmu->ssid_bits = FIELD_GET(IDR1_SSIDSIZE, reg);
>  	smmu->sid_bits = FIELD_GET(IDR1_SIDSIZE, reg);
> +	smmu->iommu.pasids = smmu->ssid_bits;
> 
>  	/*
>  	 * If the SMMU supports fewer bits than would fill a single L2 stream
> diff --git a/drivers/iommu/intel/dmar.c b/drivers/iommu/intel/dmar.c
> index 4de960834a1b..1c3cf267934d 100644
> --- a/drivers/iommu/intel/dmar.c
> +++ b/drivers/iommu/intel/dmar.c
> @@ -1126,6 +1126,10 @@ static int alloc_iommu(struct dmar_drhd_unit
> *drhd)
> 
>  	raw_spin_lock_init(&iommu->register_lock);
> 
> +	/* Supports full 20-bit PASID in scalable mode. */
> +	if (ecap_pasid(iommu->ecap))
> +		iommu->iommu.pasids = 1UL << 20;
> +

supported pasid bits is reported by ecap_pss(). I don't think we should
assume 20bits here.

>  	/*
>  	 * This is only for hotplug; at boot time intel_iommu_enabled won't
>  	 * be set yet. When intel_iommu_init() runs, it registers the units
> --
> 2.25.1