RE: [PATCH v4 06/12] iommu/vt-d: Set the nested domain to a device

From: "Tian, Kevin" <kevin.tian@intel.com>
To: "Liu, Yi L" <yi.l.liu@intel.com>,
	"joro@8bytes.org" <joro@8bytes.org>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"jgg@nvidia.com" <jgg@nvidia.com>,
	"robin.murphy@arm.com" <robin.murphy@arm.com>,
	"baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>
Cc: "cohuck@redhat.com" <cohuck@redhat.com>,
	"eric.auger@redhat.com" <eric.auger@redhat.com>,
	"nicolinc@nvidia.com" <nicolinc@nvidia.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"mjrosato@linux.ibm.com" <mjrosato@linux.ibm.com>,
	"chao.p.peng@linux.intel.com" <chao.p.peng@linux.intel.com>,
	"yi.y.sun@linux.intel.com" <yi.y.sun@linux.intel.com>,
	"peterx@redhat.com" <peterx@redhat.com>,
	"jasowang@redhat.com" <jasowang@redhat.com>,
	"shameerali.kolothum.thodi@huawei.com" 
	<shameerali.kolothum.thodi@huawei.com>,
	"lulu@redhat.com" <lulu@redhat.com>,
	"suravee.suthikulpanit@amd.com" <suravee.suthikulpanit@amd.com>,
	"iommu@lists.linux.dev" <iommu@lists.linux.dev>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-kselftest@vger.kernel.org"
	<linux-kselftest@vger.kernel.org>,
	"Duan, Zhenzhong" <zhenzhong.duan@intel.com>,
	Jacob Pan <jacob.jun.pan@linux.intel.com>
Subject: RE: [PATCH v4 06/12] iommu/vt-d: Set the nested domain to a device
Date: Wed, 2 Aug 2023 07:22:19 +0000	[thread overview]
Message-ID: <BN9PR11MB527652A8EB70FF1FEB0E74308C0BA@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20230724111335.107427-7-yi.l.liu@intel.com>

> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Monday, July 24, 2023 7:13 PM
> +
> +static int intel_nested_attach_dev(struct iommu_domain *domain,
> +				   struct device *dev)
> +{
> +	struct device_domain_info *info = dev_iommu_priv_get(dev);
> +	struct dmar_domain *dmar_domain = to_dmar_domain(domain);
> +	struct intel_iommu *iommu = info->iommu;
> +	unsigned long flags;
> +	int ret = 0;
> +
> +	if (info->domain)
> +		device_block_translation(dev);
> +
> +	if (iommu->agaw < dmar_domain->s2_domain->agaw) {
> +		dev_err_ratelimited(dev, "Adjusted guest address width not
> compatible\n");
> +		return -ENODEV;
> +	}

this is the check duplicated with patch04.

> +
> +	ret = domain_attach_iommu(dmar_domain, iommu);
> +	if (ret) {
> +		dev_err_ratelimited(dev, "Failed to attach domain to
> iommu\n");
> +		return ret;
> +	}
> +

[...]

> +	domain_update_iommu_cap(dmar_domain);

iommu_cap is already updated in domain_attach_iommu().

> 
>  static const struct iommu_domain_ops intel_nested_domain_ops = {
> +	.attach_dev		= intel_nested_attach_dev,
>  	.free			= intel_nested_domain_free,
> +	.enforce_cache_coherency = intel_iommu_enforce_cache_coherency,

this is not required. enforce_cache_coherency() will be called on parent
hwpt when it's being created. patch04 should check parent's force_snooping
to set pgsnp in the pasid entry.

As Jason explained it should be done only for kernel owned page table.