RE: [PATCH RFCv2 24/24] iommu/arm-smmu-v3: Advertise IOMMU_DOMAIN_F_ENFORCE_DIRTY

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

> -----Original Message-----
> From: Joao Martins [mailto:joao.m.martins@oracle.com]
> Sent: 18 May 2023 21:47
> To: iommu@lists.linux.dev
> Cc: Jason Gunthorpe <jgg@nvidia.com>; Kevin Tian <kevin.tian@intel.com>;
> Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>; Lu
> Baolu <baolu.lu@linux.intel.com>; Yi Liu <yi.l.liu@intel.com>; Yi Y Sun
> <yi.y.sun@intel.com>; Eric Auger <eric.auger@redhat.com>; Nicolin Chen
> <nicolinc@nvidia.com>; Joerg Roedel <joro@8bytes.org>; Jean-Philippe
> Brucker <jean-philippe@linaro.org>; Suravee Suthikulpanit
> <suravee.suthikulpanit@amd.com>; Will Deacon <will@kernel.org>; Robin
> Murphy <robin.murphy@arm.com>; Alex Williamson
> <alex.williamson@redhat.com>; kvm@vger.kernel.org; Joao Martins
> <joao.m.martins@oracle.com>
> Subject: [PATCH RFCv2 24/24] iommu/arm-smmu-v3: Advertise
> IOMMU_DOMAIN_F_ENFORCE_DIRTY
> 
> Now that we probe, and handle the DBM bit modifier, unblock
> the kAPI usage by exposing the IOMMU_DOMAIN_F_ENFORCE_DIRTY
> and implement it's requirement of revoking device attachment
> in the iommu_capable. Finally expose the IOMMU_CAP_DIRTY to
> users (IOMMUFD_DEVICE_GET_CAPS).
> 
> Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> 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 bf0aac333725..71dd95a687fd 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2014,6 +2014,8 @@ static bool arm_smmu_capable(struct device *dev,
> enum iommu_cap cap)
>  		return master->smmu->features &
> ARM_SMMU_FEAT_COHERENCY;
>  	case IOMMU_CAP_NOEXEC:
>  		return true;
> +	case IOMMU_CAP_DIRTY:
> +		return arm_smmu_dbm_capable(master->smmu);
>  	default:
>  		return false;
>  	}
> @@ -2430,6 +2432,11 @@ static int arm_smmu_attach_dev(struct
> iommu_domain *domain, struct device *dev)
>  	master = dev_iommu_priv_get(dev);
>  	smmu = master->smmu;
> 
> +	if (domain->flags & IOMMU_DOMAIN_F_ENFORCE_DIRTY &&
> +	    !arm_smmu_dbm_capable(smmu))
> +		return -EINVAL;
> +
> +

Since we have the supported_flags always set to " IOMMU_DOMAIN_F_ENFORCE_DIRTY"
below, platforms that doesn't have DBM capability will fail here, right? Or the idea is to set
domain flag only if the capability is reported true? But the iommu_domain_set_flags() doesn't
seems to check the capability though. 

(This seems to be causing problem with a rebased Qemu branch for ARM I have while sanity
testing on a platform that doesn't have DBM. I need to double check though).

Thanks,
Shameer

   
>  	/*
>  	 * Checking that SVA is disabled ensures that this device isn't bound to
>  	 * any mm, and can be safely detached from its old domain. Bonds
> cannot
> @@ -2913,6 +2920,7 @@ static void arm_smmu_remove_dev_pasid(struct
> device *dev, ioasid_t pasid)
>  }
> 
>  static struct iommu_ops arm_smmu_ops = {
> +	.supported_flags	= IOMMU_DOMAIN_F_ENFORCE_DIRTY,
>  	.capable		= arm_smmu_capable,
>  	.domain_alloc		= arm_smmu_domain_alloc,
>  	.probe_device		= arm_smmu_probe_device,
> --
> 2.17.2