linux-kernel - RE: [PATCH v5 11/11] iommu/vt-d: Disallow read-only mappings to nest parent domain

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Message-ID: <BN9PR11MB5276E140C0BFAF35D8E7CB4E8CC2A@BN9PR11MB5276.namprd11.prod.outlook.com>
Date:   Wed, 27 Sep 2023 07:04:31 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     "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>,
        "baolu.lu@...ux.intel.com" <baolu.lu@...ux.intel.com>
CC:     "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>,
        "Martins, Joao" <joao.m.martins@...cle.com>
Subject: RE: [PATCH v5 11/11] iommu/vt-d: Disallow read-only mappings to nest
 parent domain

> From: Liu, Yi L <yi.l.liu@...el.com>
> Sent: Thursday, September 21, 2023 3:55 PM
> 
> From: Lu Baolu <baolu.lu@...ux.intel.com>
> 
> When remapping hardware is configured by system software in scalable
> mode
> as Nested (PGTT=011b) and with PWSNP field Set in the PASID-table-entry,
> it may Set Accessed bit and Dirty bit (and Extended Access bit if enabled)
> in first-stage page-table entries even when second-stage mappings indicate
> that corresponding first-stage page-table is Read-Only.
> 
> As the result, contents of pages designated by VMM as Read-Only can be
> modified by IOMMU via PML5E (PML4E for 4-level tables) access as part of
> address translation process due to DMAs issued by Guest.
> 
> This disallows read-only mappings in the domain that is supposed to be used
> as nested parent. Reference from Sapphire Rapids Specification Update [1],
> errata details, SPR17. Userspace should know this limitation by checking
> the IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17 flag reported in the
> IOMMU_GET_HW_INFO
> ioctl.
> 
> [1] https://www.intel.com/content/www/us/en/content-
> details/772415/content-details.html
> 
> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
> Signed-off-by: Yi Liu <yi.l.liu@...el.com>

Reviewed-by: Kevin Tian <kevin.tian@...el.com>