On 10/20/23 5:32 PM, Yi Liu wrote:
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.
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-detai...
Reviewed-by: Kevin Tian kevin.tian@intel.com Signed-off-by: Lu Baolu baolu.lu@linux.intel.com Signed-off-by: Yi Liu yi.l.liu@intel.com
drivers/iommu/intel/iommu.c | 9 +++++++++ drivers/iommu/intel/iommu.h | 1 + include/uapi/linux/iommufd.h | 12 +++++++++++- 3 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index c7704e7efd4a..a0341a069fbf 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -2193,6 +2193,11 @@ __domain_mapping(struct dmar_domain *domain, unsigned long iov_pfn, if ((prot & (DMA_PTE_READ|DMA_PTE_WRITE)) == 0) return -EINVAL;
- if (!(prot & DMA_PTE_WRITE) && domain->is_nested_parent) {
pr_err_ratelimited("Read-only mapping is disallowed on the domain which serves as the parent in a nested configuration, due to HW errata (ERRATA_772415_SPR17)\n");return -EINVAL;- }
- attr = prot & (DMA_PTE_READ | DMA_PTE_WRITE | DMA_PTE_SNP); attr |= DMA_FL_PTE_PRESENT; if (domain->use_first_level) {
@@ -4101,6 +4106,9 @@ intel_iommu_domain_alloc_user(struct device *dev, u32 flags, domain = iommu_domain_alloc(dev->bus); if (!domain) return ERR_PTR(-ENOMEM);
container_of(domain,struct dmar_domain,domain)->is_nested_parent = request_nest_parent;
How about to_dmar_domain(domain)->is_nested_parent = ...; ?
I would also prefer to introduce is_nested_parent_domain to the user domain allocation patch (patch 7/8). This field should be checked when allocating a nested user domain.
diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c index 8f81a5c9fcc0..d3f6bc1f6590 100644 --- a/drivers/iommu/intel/iommu.c +++ b/drivers/iommu/intel/iommu.c @@ -4121,6 +4121,8 @@ intel_iommu_domain_alloc_user(struct device *dev, u32 flags, return ERR_PTR(-EINVAL); if (request_nest_parent) return ERR_PTR(-EINVAL); + if (!to_dmar_domain(parent)->is_nested_parent) + return ERR_PTR(-EINVAL);
return intel_nested_domain_alloc(parent, user_data); }
Best regards, baolu