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>,
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<linux-kselftest@vger.kernel.org>,
"Duan, Zhenzhong" <zhenzhong.duan@intel.com>
Subject: RE: [PATCH v3 10/10] iommu/vt-d: Disallow nesting on domains with read-only mappings
Date: Wed, 24 May 2023 07:44:54 +0000 [thread overview]
Message-ID: <BN9PR11MB527673E35A8C123648997A238C419@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20230511145110.27707-11-yi.l.liu@intel.com>
> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Thursday, May 11, 2023 10:51 PM
>
> From: Lu Baolu <baolu.lu@linux.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.
>
> Disallow the nested translation when there are read-only pages in the
> corresponding second-stage mappings. And, no read-only pages are allowed
> to be configured in the second-stage table of a nested translation.
> For the latter, an alternative is to disallow read-only mappings in
> any stage-2 domain as long as it's ever been used as a parent. In this
> way, we can simply replace the user counter with a flag.
>
> In concept if the user understands this errata and does expect to
> enable nested translation it should never install any RO mapping
> in stage-2 in the entire VM life cycle."
IMHO the alternative is reasonable and simpler. If the user decides to
enable nesting it should keep the nesting-friendly configuration static
since whether nesting is enabled on a device is according to viommu
configuration (i.e. whether the guest attaches the device to identity
domain or non-identity domain) and it's not good to break the nesting
setup just because the host inadvertently adds a RO mapping to s2 in
the middle between guest is detached/put back to identity domain
and then re-attach to an unmanaged domain.
>
> + if (!(prot & DMA_PTE_WRITE) && !domain->read_only_mapped) {
> + spin_lock_irqsave(&domain->lock, flags);
> + if (domain->nested_users > 0) {
> + spin_unlock_irqrestore(&domain->lock, flags);
> + return -EINVAL;
> + }
> +
this is worth a one-off warning. Same in the other path.
next prev parent reply other threads:[~2023-05-24 7:44 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-11 14:51 [PATCH v3 00/10] Add Intel VT-d nested translation Yi Liu
2023-05-11 14:51 ` [PATCH v3 01/10] iommufd: Add data structure for Intel VT-d stage-1 domain allocation Yi Liu
2023-05-24 6:59 ` Tian, Kevin
2023-05-25 2:28 ` Zhang, Tina
2023-05-29 20:00 ` Jason Gunthorpe
2023-05-29 19:53 ` Jason Gunthorpe
2023-05-11 14:51 ` [PATCH v3 02/10] iommu/vt-d: Extend dmar_domain to support nested domain Yi Liu
2023-05-24 7:02 ` Tian, Kevin
2023-05-26 2:56 ` Baolu Lu
2023-05-11 14:51 ` [PATCH v3 03/10] iommu/vt-d: Add helper for nested domain allocation Yi Liu
2023-05-11 14:51 ` [PATCH v3 04/10] iommu/vt-d: Add helper to setup pasid nested translation Yi Liu
2023-05-24 7:16 ` Tian, Kevin
2023-05-26 4:16 ` Baolu Lu
2023-06-07 8:34 ` Liu, Yi L
2023-06-08 3:32 ` Liu, Yi L
2023-06-08 3:35 ` Liu, Yi L
2023-06-08 3:37 ` Baolu Lu
2023-05-11 14:51 ` [PATCH v3 05/10] iommu/vt-d: Make domain attach helpers to be extern Yi Liu
2023-05-11 14:51 ` [PATCH v3 06/10] iommu/vt-d: Set the nested domain to a device Yi Liu
2023-05-24 7:22 ` Tian, Kevin
2023-05-26 4:24 ` Baolu Lu
2023-05-11 14:51 ` [PATCH v3 07/10] iommu/vt-d: Add iotlb flush for nested domain Yi Liu
2023-05-24 7:33 ` Tian, Kevin
2023-06-08 7:14 ` Liu, Yi L
2023-06-08 8:07 ` Baolu Lu
2023-06-20 6:22 ` Liu, Yi L
2023-05-11 14:51 ` [PATCH v3 08/10] iommu/vt-d: Add nested domain allocation Yi Liu
2023-05-11 14:51 ` [PATCH v3 09/10] iommu/vt-d: Implement hw_info for iommu capability query Yi Liu
2023-05-11 14:51 ` [PATCH v3 10/10] iommu/vt-d: Disallow nesting on domains with read-only mappings Yi Liu
2023-05-24 7:44 ` Tian, Kevin [this message]
2023-05-26 4:28 ` Baolu Lu
2023-05-24 8:59 ` [PATCH v3 00/10] Add Intel VT-d nested translation Tian, Kevin
2023-05-25 18:06 ` Alex Williamson
2023-05-26 11:25 ` Tian, Kevin
2023-05-29 18:43 ` Jason Gunthorpe
2023-05-30 0:16 ` Alex Williamson
2023-05-30 16:42 ` Jason Gunthorpe
2023-06-14 8:07 ` Tian, Kevin
2023-06-14 11:52 ` Jason Gunthorpe
2023-06-16 2:29 ` Tian, Kevin
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