linux-kernel - Re: [PATCH v4 06/15] iommu/vt-d: Support setting ioasid set to domain

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Date:   Mon, 6 Jul 2020 16:52:14 +0200
From:   Auger Eric <eric.auger@...hat.com>
To:     Liu Yi L <yi.l.liu@...el.com>, alex.williamson@...hat.com,
        baolu.lu@...ux.intel.com, joro@...tes.org
Cc:     kevin.tian@...el.com, jacob.jun.pan@...ux.intel.com,
        ashok.raj@...el.com, jun.j.tian@...el.com, yi.y.sun@...el.com,
        jean-philippe@...aro.org, peterx@...hat.com, hao.wu@...el.com,
        stefanha@...il.com, iommu@...ts.linux-foundation.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 06/15] iommu/vt-d: Support setting ioasid set to domain

Hi Yi,

On 7/4/20 1:26 PM, Liu Yi L wrote:
> From IOMMU p.o.v., PASIDs allocated and managed by external components
> (e.g. VFIO) will be passed in for gpasid_bind/unbind operation. IOMMU
> needs some knowledge to check the PASID ownership, hence add an interface
> for those components to tell the PASID owner.
> 
> In latest kernel design, PASID ownership is managed by IOASID set where
> the PASID is allocated from. This patch adds support for setting ioasid
> set ID to the domains used for nesting/vSVA. Subsequent SVA operations
> on the PASID will be checked against its IOASID set for proper ownership.
> 
> Cc: Kevin Tian <kevin.tian@...el.com>
> CC: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> Cc: Alex Williamson <alex.williamson@...hat.com>
> Cc: Eric Auger <eric.auger@...hat.com>
> Cc: Jean-Philippe Brucker <jean-philippe@...aro.org>
> Cc: Joerg Roedel <joro@...tes.org>
> Cc: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Liu Yi L <yi.l.liu@...el.com>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  drivers/iommu/intel/iommu.c | 16 ++++++++++++++++
>  include/linux/intel-iommu.h |  4 ++++
>  include/linux/iommu.h       |  1 +
>  3 files changed, 21 insertions(+)
> 
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index 62ebe01..89d708d 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -1793,6 +1793,7 @@ static struct dmar_domain *alloc_domain(int flags)
>  	if (first_level_by_default())
>  		domain->flags |= DOMAIN_FLAG_USE_FIRST_LEVEL;
>  	domain->has_iotlb_device = false;
> +	domain->ioasid_sid = INVALID_IOASID_SET;
>  	INIT_LIST_HEAD(&domain->devices);
>  
>  	return domain;
> @@ -6039,6 +6040,21 @@ intel_iommu_domain_set_attr(struct iommu_domain *domain,
>  		}
>  		spin_unlock_irqrestore(&device_domain_lock, flags);
>  		break;
> +	case DOMAIN_ATTR_IOASID_SID:
no need to take the device_domain_lock?
> +		if (!(dmar_domain->flags & DOMAIN_FLAG_NESTING_MODE)) {
> +			ret = -ENODEV;
> +			break;
> +		}
> +		if ((dmar_domain->ioasid_sid != INVALID_IOASID_SET) &&
> +		    (dmar_domain->ioasid_sid != (*(int *) data))) {
storing *(int *) data) in a local variable would increase the
readability of the code I think.
> +			pr_warn_ratelimited("multi ioasid_set (%d:%d) setting",
> +					    dmar_domain->ioasid_sid,
> +					    (*(int *) data));
> +			ret = -EBUSY;
> +			break;
> +		}
> +		dmar_domain->ioasid_sid = *(int *) data;
> +		break;
>  	default:
>  		ret = -EINVAL;
>  		break;
> diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
> index 3f23c26..0d0ab32 100644
> --- a/include/linux/intel-iommu.h
> +++ b/include/linux/intel-iommu.h
> @@ -549,6 +549,10 @@ struct dmar_domain {
>  					   2 == 1GiB, 3 == 512GiB, 4 == 1TiB */
>  	u64		max_addr;	/* maximum mapped address */
>  
> +	int		ioasid_sid;	/*
> +					 * the ioasid set which tracks all
> +					 * PASIDs used by the domain.
> +					 */
>  	int		default_pasid;	/*
>  					 * The default pasid used for non-SVM
>  					 * traffic on mediated devices.
> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
> index 2567c33..21d32be 100644
> --- a/include/linux/iommu.h
> +++ b/include/linux/iommu.h
> @@ -124,6 +124,7 @@ enum iommu_attr {
>  	DOMAIN_ATTR_FSL_PAMUV1,
>  	DOMAIN_ATTR_NESTING,	/* two stages of translation */
>  	DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE,
> +	DOMAIN_ATTR_IOASID_SID,
>  	DOMAIN_ATTR_MAX,
>  };
>  
> 
Thanks

Eric