[PATCH v6 09/13] iommu/amd: Add support for nested domain allocation

Suravee Suthikulpanit
2026-01-15T06:09:32Z

The nested domain is allocated with IOMMU_DOMAIN_NESTED type to store
stage-1 translation (i.e. GVA->GPA). This includes the GCR3 root pointer
table along with guest page tables. The struct iommu_hwpt_amd_guest
contains this information, and is passed from user-space as a parameter
of the struct iommu_ops.domain_alloc_nested().

Reviewed-by: Nicolin Chen <nicolinc@nvidia.com>
Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
drivers/iommu/amd/Makefile | 2 +-
drivers/iommu/amd/amd_iommu.h | 4 +
drivers/iommu/amd/amd_iommu_types.h | 14 ++++
drivers/iommu/amd/nested.c | 110 ++++++++++++++++++++++++++++
4 files changed, 129 insertions(+), 1 deletion(-)
create mode 100644 drivers/iommu/amd/nested.c

diff --git a/drivers/iommu/amd/Makefile b/drivers/iommu/amd/Makefile
index 41f053b49dce..94b8ef2acb18 100644
--- a/drivers/iommu/amd/Makefile
+++ b/drivers/iommu/amd/Makefile
@@ -1,4 +1,4 @@
# SPDX-License-Identifier: GPL-2.0-only
obj-y += iommu.o init.o quirks.o ppr.o pasid.o
-obj-$(CONFIG_AMD_IOMMU_IOMMUFD) += iommufd.o
+obj-$(CONFIG_AMD_IOMMU_IOMMUFD) += iommufd.o nested.o
obj-$(CONFIG_AMD_IOMMU_DEBUGFS) += debugfs.o
diff --git a/drivers/iommu/amd/amd_iommu.h b/drivers/iommu/amd/amd_iommu.h
index d97b9b6d76d3..aa29afe96e90 100644
--- a/drivers/iommu/amd/amd_iommu.h
+++ b/drivers/iommu/amd/amd_iommu.h
@@ -202,4 +202,8 @@ amd_iommu_make_clear_dte(struct iommu_dev_data *dev_data, struct dev_table_entry
new->data128[1] = 0;
}

+/* NESTED */
+struct iommu_domain *
+amd_iommu_alloc_domain_nested(struct iommufd_viommu *viommu, u32 flags,
+ const struct iommu_user_data *user_data);
#endif /* AMD_IOMMU_H */
diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index d5b3393ab3a9..487ee6123de5 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -21,6 +21,8 @@
#include <linux/irqreturn.h>
#include <linux/generic_pt/iommu.h>

+#include <uapi/linux/iommufd.h>
+
/*
* Maximum number of IOMMUs supported
*/
@@ -353,6 +355,8 @@
#define DTE_FLAG_V BIT_ULL(0)
#define DTE_FLAG_TV BIT_ULL(1)
#define DTE_FLAG_HAD (3ULL << 7)
+#define DTE_MODE_MASK GENMASK_ULL(11, 9)
+#define DTE_HOST_TRP GENMASK_ULL(51, 12)
#define DTE_FLAG_GIOV BIT_ULL(54)
#define DTE_FLAG_GV BIT_ULL(55)
#define DTE_GLX GENMASK_ULL(57, 56)
@@ -501,6 +505,16 @@ struct amd_iommu_viommu {
struct protection_domain *parent; /* nest parent domain for this viommu */
};

+/*
+ * Nested domain is specifically used for nested translation
+ */
+struct nested_domain {
+ struct iommu_domain domain; /* generic domain handle used by iommu core code */
+ u16 gdom_id; /* domain ID from gDTE */
+ struct iommu_hwpt_amd_guest gdte; /* Guest vIOMMU DTE */
+ struct amd_iommu_viommu *viommu; /* AMD hw-viommu this nested domain belong to */
+};
+
/*
* This structure contains generic data for IOMMU protection domains
* independent of their use.
diff --git a/drivers/iommu/amd/nested.c b/drivers/iommu/amd/nested.c
new file mode 100644
index 000000000000..a8c0bb4dd733
--- /dev/null
+++ b/drivers/iommu/amd/nested.c
@@ -0,0 +1,110 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 Advanced Micro Devices, Inc.
+ */
+
+#define dev_fmt(fmt) "AMD-Vi: " fmt
+
+#include <linux/iommu.h>
+#include <uapi/linux/iommufd.h>
+
+#include "amd_iommu.h"
+
+static const struct iommu_domain_ops nested_domain_ops;
+
+static inline struct nested_domain *to_ndomain(struct iommu_domain *dom)
+{
+ return container_of(dom, struct nested_domain, domain);
+}
+
+/*
+ * Validate guest DTE to make sure that configuration for host (v1)
+ * and guest (v2) page tables are valid when allocating nested domain.
+ */
+static int validate_gdte_nested(struct iommu_hwpt_amd_guest *gdte)
+{
+ u32 gpt_level = FIELD_GET(DTE_GPT_LEVEL_MASK, gdte->dte[2]);
+
+ /* Must be zero: Mode, Host-TPR */
+ if (FIELD_GET(DTE_MODE_MASK, gdte->dte[0]) != 0 ||
+ FIELD_GET(DTE_HOST_TRP, gdte->dte[0]) != 0)
+ return -EINVAL;
+
+ /* GCR3 TRP must be non-zero if V, GV is set */
+ if (FIELD_GET(DTE_FLAG_V, gdte->dte[0]) == 1 &&
+ FIELD_GET(DTE_FLAG_GV, gdte->dte[0]) == 1 &&
+ FIELD_GET(DTE_GCR3_14_12, gdte->dte[0]) == 0 &&
+ FIELD_GET(DTE_GCR3_30_15, gdte->dte[1]) == 0 &&
+ FIELD_GET(DTE_GCR3_51_31, gdte->dte[1]) == 0)
+ return -EINVAL;
+
+ /* Valid Guest Paging Mode values are 0 and 1 */
+ if (gpt_level != GUEST_PGTABLE_4_LEVEL &&
+ gpt_level != GUEST_PGTABLE_5_LEVEL)
+ return -EINVAL;
+
+ /* GLX = 3 is reserved */
+ if (FIELD_GET(DTE_GLX, gdte->dte[0]) == 3)
+ return -EINVAL;
+
+ /*
+ * We need to check host capability before setting
+ * the Guest Paging Mode
+ */
+ if (gpt_level == GUEST_PGTABLE_5_LEVEL &&
+ amd_iommu_gpt_level < PAGE_MODE_5_LEVEL)
+ return -EOPNOTSUPP;
+
+ return 0;
+}
+
+/*
+ * This function is assigned to struct iommufd_viommu_ops.alloc_domain_nested()
+ * during the call to struct iommu_ops.viommu_init().
+ */
+struct iommu_domain *
+amd_iommu_alloc_domain_nested(struct iommufd_viommu *viommu, u32 flags,
+ const struct iommu_user_data *user_data)
+{
+ int ret;
+ struct nested_domain *ndom;
+ struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
+
+ if (user_data->type != IOMMU_HWPT_DATA_AMD_GUEST)
+ return ERR_PTR(-EOPNOTSUPP);
+
+ ndom = kzalloc(sizeof(*ndom), GFP_KERNEL);
+ if (!ndom)
+ return ERR_PTR(-ENOMEM);
+
+ ret = iommu_copy_struct_from_user(&ndom->gdte, user_data,
+ IOMMU_HWPT_DATA_AMD_GUEST,
+ dte);
+ if (ret)
+ goto out_err;
+
+ ret = validate_gdte_nested(&ndom->gdte);
+ if (ret)
+ goto out_err;
+
+ ndom->gdom_id = FIELD_GET(DTE_DOMID_MASK, ndom->gdte.dte[1]);
+ ndom->domain.ops = &nested_domain_ops;
+ ndom->domain.type = IOMMU_DOMAIN_NESTED;
+ ndom->viommu = aviommu;
+
+ return &ndom->domain;
+out_err:
+ kfree(ndom);
+ return ERR_PTR(ret);
+}
+
+static void nested_domain_free(struct iommu_domain *dom)
+{
+ struct nested_domain *ndom = to_ndomain(dom);
+
+ kfree(ndom);
+}
+
+static const struct iommu_domain_ops nested_domain_ops = {
+ .free = nested_domain_free,
+};
--
2.34.1