[v7,8/8] iommu/vt-d: Disallow read-only mappings to nest parent domain
Commit Message
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-details.html
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 | 6 ++++++
include/uapi/linux/iommufd.h | 12 +++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)
Comments
> From: Liu, Yi L <yi.l.liu@intel.com>
> Sent: Tuesday, October 24, 2023 11:14 PM
>
> +/**
> + * enum iommu_hw_info_vtd_flags - Flags for VT-d hw_info
> + * @IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17: If set, disallow
> nesting on domains
> + * with read-only mapping.
with how it's implemented now the description should be revised to:
"If set, disallow read-only mappings on a nested_parent domain"
On 2023/10/25 15:35, Tian, Kevin wrote:
>> From: Liu, Yi L <yi.l.liu@intel.com>
>> Sent: Tuesday, October 24, 2023 11:14 PM
>>
>> +/**
>> + * enum iommu_hw_info_vtd_flags - Flags for VT-d hw_info
>> + * @IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17: If set, disallow
>> nesting on domains
>> + * with read-only mapping.
>
> with how it's implemented now the description should be revised to:
>
> "If set, disallow read-only mappings on a nested_parent domain"
sure.
@@ -2194,6 +2194,11 @@ __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->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) {
@@ -4872,6 +4877,7 @@ static void *intel_iommu_hw_info(struct device *dev, u32 *length, u32 *type)
if (!vtd)
return ERR_PTR(-ENOMEM);
+ vtd->flags = IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17;
vtd->cap_reg = iommu->cap;
vtd->ecap_reg = iommu->ecap;
*length = sizeof(*vtd);
@@ -444,10 +444,20 @@ struct iommu_hwpt_alloc {
};
#define IOMMU_HWPT_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_HWPT_ALLOC)
+/**
+ * enum iommu_hw_info_vtd_flags - Flags for VT-d hw_info
+ * @IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17: If set, disallow nesting on domains
+ * with read-only mapping.
+ * https://www.intel.com/content/www/us/en/content-details/772415/content-details.html
+ */
+enum iommu_hw_info_vtd_flags {
+ IOMMU_HW_INFO_VTD_ERRATA_772415_SPR17 = 1 << 0,
+};
+
/**
* struct iommu_hw_info_vtd - Intel VT-d hardware information
*
- * @flags: Must be 0
+ * @flags: Combination of enum iommu_hw_info_vtd_flags
* @__reserved: Must be 0
*
* @cap_reg: Value of Intel VT-d capability register defined in VT-d spec