On 10/20/23 5:32 PM, Yi Liu wrote:
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
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Signed-off-by: Yi Liu <yi.l.liu@xxxxxxxxx>
---
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
