[PATCH v2 6/8] iommu/arm-smmu-v3: Support IOMMU_GET_HW_INFO via struct arm_smmu_hw_info

Jason Gunthorpe
2024-08-27T15:56:09Z

From: Nicolin Chen <nicolinc@nvidia.com>

For virtualization cases the IDR/IIDR/AIDR values of the actual SMMU
instance need to be available to the VMM so it can construct an
appropriate vSMMUv3 that reflects the correct HW capabilities.

For userspace page tables these values are required to constrain the valid
values within the CD table and the IOPTEs.

The kernel does not sanitize these values. If building a VMM then
userspace is required to only forward bits into a VM that it knows it can
implement. Some bits will also require a VMM to detect if appropriate
kernel support is available such as for ATS and BTM.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 24 ++++++++++++++
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 2 ++
include/uapi/linux/iommufd.h | 35 +++++++++++++++++++++
3 files changed, 61 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index c2021e821e5cb6..ec2fcdd4523a26 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2288,6 +2288,29 @@ static bool arm_smmu_enforce_cache_coherency(struct iommu_domain *domain)
return ret;
}

+static void *arm_smmu_hw_info(struct device *dev, u32 *length, u32 *type)
+{
+ struct arm_smmu_master *master = dev_iommu_priv_get(dev);
+ struct iommu_hw_info_arm_smmuv3 *info;
+ u32 __iomem *base_idr;
+ unsigned int i;
+
+ info = kzalloc(sizeof(*info), GFP_KERNEL);
+ if (!info)
+ return ERR_PTR(-ENOMEM);
+
+ base_idr = master->smmu->base + ARM_SMMU_IDR0;
+ for (i = 0; i <= 5; i++)
+ info->idr[i] = readl_relaxed(base_idr + i);
+ info->iidr = readl_relaxed(master->smmu->base + ARM_SMMU_IIDR);
+ info->aidr = readl_relaxed(master->smmu->base + ARM_SMMU_AIDR);
+
+ *length = sizeof(*info);
+ *type = IOMMU_HW_INFO_TYPE_ARM_SMMUV3;
+
+ return info;
+}
+
struct arm_smmu_domain *arm_smmu_domain_alloc(void)
{
struct arm_smmu_domain *smmu_domain;
@@ -3467,6 +3490,7 @@ static struct iommu_ops arm_smmu_ops = {
.identity_domain = &arm_smmu_identity_domain,
.blocked_domain = &arm_smmu_blocked_domain,
.capable = arm_smmu_capable,
+ .hw_info = arm_smmu_hw_info,
.domain_alloc_paging = arm_smmu_domain_alloc_paging,
.domain_alloc_sva = arm_smmu_sva_domain_alloc,
.domain_alloc_user = arm_smmu_domain_alloc_user,
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 45882f65bfcad0..4b05c81b181a82 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -80,6 +80,8 @@
#define IIDR_REVISION GENMASK(15, 12)
#define IIDR_IMPLEMENTER GENMASK(11, 0)

+#define ARM_SMMU_AIDR 0x1C
+
#define ARM_SMMU_CR0 0x20
#define CR0_ATSCHK (1 << 4)
#define CR0_CMDQEN (1 << 3)
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 4dde745cfb7e29..83b6e1cd338d8f 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -484,15 +484,50 @@ struct iommu_hw_info_vtd {
__aligned_u64 ecap_reg;
};

+/**
+ * struct iommu_hw_info_arm_smmuv3 - ARM SMMUv3 hardware information
+ * (IOMMU_HW_INFO_TYPE_ARM_SMMUV3)
+ *
+ * @flags: Must be set to 0
+ * @__reserved: Must be 0
+ * @idr: Implemented features for ARM SMMU Non-secure programming interface
+ * @iidr: Information about the implementation and implementer of ARM SMMU,
+ * and architecture version supported
+ * @aidr: ARM SMMU architecture version
+ *
+ * For the details of @idr, @iidr and @aidr, please refer to the chapters
+ * from 6.3.1 to 6.3.6 in the SMMUv3 Spec.
+ *
+ * User space should read the underlying ARM SMMUv3 hardware information for
+ * the list of supported features.
+ *
+ * Note that these values reflect the raw HW capability, without any insight if
+ * any required kernel driver support is present. Bits may be set indicating the
+ * HW has functionality that is lacking kernel software support, such as BTM. If
+ * a VMM is using this information to construct emulated copies of these
+ * registers it should only forward bits that it knows it can support.
+ *
+ * In future, presence of required kernel support will be indicated in flags.
+ */
+struct iommu_hw_info_arm_smmuv3 {
+ __u32 flags;
+ __u32 __reserved;
+ __u32 idr[6];
+ __u32 iidr;
+ __u32 aidr;
+};
+
/**
* enum iommu_hw_info_type - IOMMU Hardware Info Types
* @IOMMU_HW_INFO_TYPE_NONE: Used by the drivers that do not report hardware
* info
* @IOMMU_HW_INFO_TYPE_INTEL_VTD: Intel VT-d iommu info type
+ * @IOMMU_HW_INFO_TYPE_ARM_SMMUV3: ARM SMMUv3 iommu info type
*/
enum iommu_hw_info_type {
IOMMU_HW_INFO_TYPE_NONE = 0,
IOMMU_HW_INFO_TYPE_INTEL_VTD = 1,
+ IOMMU_HW_INFO_TYPE_ARM_SMMUV3 = 2,
};

/**
--
2.46.0