linux-kernel - Re: [PATCH v4 04/12] iommu/vt-d: Add helper to setup pasid nested translation

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Message-ID: <d57dc99c-4970-fe0f-53f9-ea6f926910ca@linux.intel.com>
Date:   Thu, 3 Aug 2023 11:13:14 +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 04/12] iommu/vt-d: Add helper to setup pasid nested
 translation

On 2023/8/2 15:10, Tian, Kevin wrote:
>> From: Liu, Yi L<yi.l.liu@...el.com>
>> Sent: Monday, July 24, 2023 7:13 PM
>>   }
>> +
>> +/**
>> + * intel_pasid_setup_nested() - Set up PASID entry for nested translation.
>> + * This could be used for nested translation based vIOMMU. e.g. guest IOVA
> s/could be/is/

Ack.

> 
>> + * and guest shared virtual address. In this case, the first level page
>> + * tables are used for GVA/GIOVA-GPA translation in the guest, second level
>> + * page tables are used for GPA-HPA translation.
> let's be consistent on using stage-1/stage-2
> 
> btw the convention is to have 1-line summary, then the list of
> parameters followed by detail explanation of the function.
> 

This patch just follows the existing code style in this file. Need a
separated patch to cleanup this.

>> + *
>> + * @iommu:      IOMMU which the device belong to
>> + * @dev:        Device to be set up for translation
>> + * @pasid:      PASID to be programmed in the device PASID table
>> + * @domain:     User stage-1 domain nested on a s2 domain
>> + */
>> +int intel_pasid_setup_nested(struct intel_iommu *iommu, struct device
>> *dev,
>> +			     u32 pasid, struct dmar_domain *domain)
>> +{
>> +	struct iommu_hwpt_vtd_s1 *s1_cfg = &domain->s1_cfg;
>> +	pgd_t *s1_gpgd = (pgd_t *)(uintptr_t)domain->s1_pgtbl;
>> +	struct dmar_domain *s2_domain = domain->s2_domain;
>> +	u16 did = domain_id_iommu(domain, iommu);
>> +	struct dma_pte *pgd = s2_domain->pgd;
>> +	struct pasid_entry *pte;
>> +
>> +	if (!ecap_nest(iommu->ecap)) {
>> +		pr_err_ratelimited("%s: No nested translation support\n",
>> +				   iommu->name);
>> +		return -ENODEV;
>> +	}
> -EINVAL

This is in the attach domain path. -EINVAL has the special meaning of
"this domain is not compatible with iommu for the device".

So here, I still think we should return -ENODEV and the caller doesn't
need to retry anymore.

> 
>> +
>> +	if (s2_domain->agaw > iommu->agaw) {
>> +		pr_err_ratelimited("Incompatible agaw %s\n", iommu-
>>> name);
>> +		return -EINVAL;
>> +	}
> there is a duplicated check in intel_nested_attach_dev().
> 

Yeah, should be removed.

Best regards,
baolu