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

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Thursday, September 21, 2023 3:55 PM
> 
> From: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> 
> 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@xxxxxxxxxxxxxxx>
> Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>

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