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

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Date:   Thu, 3 Aug 2023 11:17:49 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        "Liu, Yi L" <yi.l.liu@...el.com>,
        "joro@...tes.org" <joro@...tes.org>,
        "alex.williamson@...hat.com" <alex.williamson@...hat.com>,
        "jgg@...dia.com" <jgg@...dia.com>,
        "robin.murphy@....com" <robin.murphy@....com>
Cc:     baolu.lu@...ux.intel.com, "cohuck@...hat.com" <cohuck@...hat.com>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "nicolinc@...dia.com" <nicolinc@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "mjrosato@...ux.ibm.com" <mjrosato@...ux.ibm.com>,
        "chao.p.peng@...ux.intel.com" <chao.p.peng@...ux.intel.com>,
        "yi.y.sun@...ux.intel.com" <yi.y.sun@...ux.intel.com>,
        "peterx@...hat.com" <peterx@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "shameerali.kolothum.thodi@...wei.com" 
        <shameerali.kolothum.thodi@...wei.com>,
        "lulu@...hat.com" <lulu@...hat.com>,
        "suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "Duan, Zhenzhong" <zhenzhong.duan@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: Re: [PATCH v4 06/12] iommu/vt-d: Set the nested domain to a device

On 2023/8/2 15:22, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@...el.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.

Ack. No need for a check here.

> 
>> +
>> +	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().

Ack. We will eventually remove this helper when every domain is
allocated for a specific device.

>>
>>   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.

Ack and thanks!

Best regards,
baolu